diff --git a/homeassistant/components/mqtt/discovery.py b/homeassistant/components/mqtt/discovery.py
index e6350179571..ac20ba7a4a8 100644
--- a/homeassistant/components/mqtt/discovery.py
+++ b/homeassistant/components/mqtt/discovery.py
@@ -11,7 +11,7 @@ from homeassistant.helpers.dispatcher import async_dispatcher_send
 from homeassistant.helpers.typing import HomeAssistantType
 
 from .abbreviations import ABBREVIATIONS, DEVICE_ABBREVIATIONS
-from .const import ATTR_DISCOVERY_HASH, ATTR_DISCOVERY_TOPIC, CONF_STATE_TOPIC
+from .const import ATTR_DISCOVERY_HASH, ATTR_DISCOVERY_TOPIC
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -50,15 +50,6 @@ CONFIG_ENTRY_COMPONENTS = [
     "vacuum",
 ]
 
-DEPRECATED_PLATFORM_TO_SCHEMA = {
-    "light": {"mqtt_json": "json", "mqtt_template": "template"}
-}
-
-# These components require state_topic to be set.
-# If not specified, infer state_topic from discovery topic.
-IMPLICIT_STATE_TOPIC_COMPONENTS = ["alarm_control_panel", "binary_sensor", "sensor"]
-
-
 ALREADY_DISCOVERED = "mqtt_discovered_components"
 DATA_CONFIG_ENTRY_LOCK = "mqtt_config_entry_lock"
 CONFIG_ENTRY_IS_SETUP = "mqtt_config_entry_is_setup"
@@ -143,39 +134,8 @@ async def async_start(
             }
             setattr(payload, "discovery_data", discovery_data)
 
-            if CONF_PLATFORM in payload and "schema" not in payload:
-                platform = payload[CONF_PLATFORM]
-                if (
-                    component in DEPRECATED_PLATFORM_TO_SCHEMA
-                    and platform in DEPRECATED_PLATFORM_TO_SCHEMA[component]
-                ):
-                    schema = DEPRECATED_PLATFORM_TO_SCHEMA[component][platform]
-                    payload["schema"] = schema
-                    _LOGGER.warning(
-                        '"platform": "%s" is deprecated, ' 'replace with "schema":"%s"',
-                        platform,
-                        schema,
-                    )
             payload[CONF_PLATFORM] = "mqtt"
 
-            if (
-                CONF_STATE_TOPIC not in payload
-                and component in IMPLICIT_STATE_TOPIC_COMPONENTS
-            ):
-                # state_topic not specified, infer from discovery topic
-                fmt_node_id = f"{node_id}/" if node_id else ""
-                payload[
-                    CONF_STATE_TOPIC
-                ] = f"{discovery_topic}/{component}/{fmt_node_id}{object_id}/state"
-                _LOGGER.warning(
-                    'implicit %s is deprecated, add "%s":"%s" to '
-                    "%s discovery message",
-                    CONF_STATE_TOPIC,
-                    CONF_STATE_TOPIC,
-                    payload[CONF_STATE_TOPIC],
-                    topic,
-                )
-
         if ALREADY_DISCOVERED not in hass.data:
             hass.data[ALREADY_DISCOVERED] = {}
         if discovery_hash in hass.data[ALREADY_DISCOVERED]:
diff --git a/homeassistant/components/mqtt/sensor.py b/homeassistant/components/mqtt/sensor.py
index 07910697d21..7be923927ca 100644
--- a/homeassistant/components/mqtt/sensor.py
+++ b/homeassistant/components/mqtt/sensor.py
@@ -1,6 +1,5 @@
 """Support for MQTT sensors."""
 from datetime import timedelta
-import json
 import logging
 from typing import Optional
 
@@ -41,7 +40,6 @@ from .discovery import MQTT_DISCOVERY_NEW, clear_discovery_hash
 _LOGGER = logging.getLogger(__name__)
 
 CONF_EXPIRE_AFTER = "expire_after"
-CONF_JSON_ATTRS = "json_attributes"
 
 DEFAULT_NAME = "MQTT Sensor"
 DEFAULT_FORCE_UPDATE = False
@@ -53,7 +51,6 @@ PLATFORM_SCHEMA = (
             vol.Optional(CONF_EXPIRE_AFTER): cv.positive_int,
             vol.Optional(CONF_FORCE_UPDATE, default=DEFAULT_FORCE_UPDATE): cv.boolean,
             vol.Optional(CONF_ICON): cv.icon,
-            vol.Optional(CONF_JSON_ATTRS, default=[]): cv.ensure_list_csv,
             vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
             vol.Optional(CONF_UNIQUE_ID): cv.string,
             vol.Optional(CONF_UNIT_OF_MEASUREMENT): cv.string,
@@ -110,16 +107,9 @@ class MqttSensor(
         self._state = None
         self._sub_state = None
         self._expiration_trigger = None
-        self._attributes = None
 
         device_config = config.get(CONF_DEVICE)
 
-        if config.get(CONF_JSON_ATTRS):
-            _LOGGER.warning(
-                'configuration variable "json_attributes" is '
-                'deprecated, replace with "json_attributes_topic"'
-            )
-
         MqttAttributes.__init__(self, config)
         MqttAvailability.__init__(self, config)
         MqttDiscoveryUpdate.__init__(self, discovery_data, self.discovery_update)
@@ -165,22 +155,6 @@ class MqttSensor(
                     self.hass, self.value_is_expired, expiration_at
                 )
 
-            json_attributes = set(self._config[CONF_JSON_ATTRS])
-            if json_attributes:
-                self._attributes = {}
-                try:
-                    json_dict = json.loads(payload)
-                    if isinstance(json_dict, dict):
-                        attrs = {
-                            k: json_dict[k] for k in json_attributes & json_dict.keys()
-                        }
-                        self._attributes = attrs
-                    else:
-                        _LOGGER.warning("JSON result was not a dictionary")
-                except ValueError:
-                    _LOGGER.warning("MQTT payload could not be parsed as JSON")
-                    _LOGGER.debug("Erroneous JSON: %s", payload)
-
             if template is not None:
                 payload = template.async_render_with_possible_json_value(
                     payload, self._state
@@ -241,11 +215,6 @@ class MqttSensor(
         """Return the state of the entity."""
         return self._state
 
-    @property
-    def device_state_attributes(self):
-        """Return the state attributes."""
-        return self._attributes
-
     @property
     def unique_id(self):
         """Return a unique ID."""
diff --git a/tests/components/mqtt/test_discovery.py b/tests/components/mqtt/test_discovery.py
index 4a28b95e32c..8c925bdf315 100644
--- a/tests/components/mqtt/test_discovery.py
+++ b/tests/components/mqtt/test_discovery.py
@@ -117,7 +117,9 @@ async def test_correct_config_discovery(hass, mqtt_mock, caplog):
     await async_start(hass, "homeassistant", {}, entry)
 
     async_fire_mqtt_message(
-        hass, "homeassistant/binary_sensor/bla/config", '{ "name": "Beer" }'
+        hass,
+        "homeassistant/binary_sensor/bla/config",
+        '{ "name": "Beer", "state_topic": "test-topic" }',
     )
     await hass.async_block_till_done()
 
@@ -199,7 +201,9 @@ async def test_discovery_incl_nodeid(hass, mqtt_mock, caplog):
     await async_start(hass, "homeassistant", {}, entry)
 
     async_fire_mqtt_message(
-        hass, "homeassistant/binary_sensor/my_node_id/bla/config", '{ "name": "Beer" }',
+        hass,
+        "homeassistant/binary_sensor/my_node_id/bla/config",
+        '{ "name": "Beer", "state_topic": "test-topic" }',
     )
     await hass.async_block_till_done()
 
@@ -217,10 +221,14 @@ async def test_non_duplicate_discovery(hass, mqtt_mock, caplog):
     await async_start(hass, "homeassistant", {}, entry)
 
     async_fire_mqtt_message(
-        hass, "homeassistant/binary_sensor/bla/config", '{ "name": "Beer" }'
+        hass,
+        "homeassistant/binary_sensor/bla/config",
+        '{ "name": "Beer", "state_topic": "test-topic" }',
     )
     async_fire_mqtt_message(
-        hass, "homeassistant/binary_sensor/bla/config", '{ "name": "Beer" }'
+        hass,
+        "homeassistant/binary_sensor/bla/config",
+        '{ "name": "Beer", "state_topic": "test-topic" }',
     )
     await hass.async_block_till_done()
 
@@ -240,7 +248,9 @@ async def test_removal(hass, mqtt_mock, caplog):
     await async_start(hass, "homeassistant", {}, entry)
 
     async_fire_mqtt_message(
-        hass, "homeassistant/binary_sensor/bla/config", '{ "name": "Beer" }'
+        hass,
+        "homeassistant/binary_sensor/bla/config",
+        '{ "name": "Beer", "state_topic": "test-topic" }',
     )
     await hass.async_block_till_done()
     state = hass.states.get("binary_sensor.beer")
@@ -259,7 +269,9 @@ async def test_rediscover(hass, mqtt_mock, caplog):
     await async_start(hass, "homeassistant", {}, entry)
 
     async_fire_mqtt_message(
-        hass, "homeassistant/binary_sensor/bla/config", '{ "name": "Beer" }'
+        hass,
+        "homeassistant/binary_sensor/bla/config",
+        '{ "name": "Beer", "state_topic": "test-topic" }',
     )
     await hass.async_block_till_done()
     state = hass.states.get("binary_sensor.beer")
@@ -271,7 +283,9 @@ async def test_rediscover(hass, mqtt_mock, caplog):
     assert state is None
 
     async_fire_mqtt_message(
-        hass, "homeassistant/binary_sensor/bla/config", '{ "name": "Beer" }'
+        hass,
+        "homeassistant/binary_sensor/bla/config",
+        '{ "name": "Beer", "state_topic": "test-topic" }',
     )
     await hass.async_block_till_done()
     state = hass.states.get("binary_sensor.beer")
@@ -285,7 +299,9 @@ async def test_duplicate_removal(hass, mqtt_mock, caplog):
     await async_start(hass, "homeassistant", {}, entry)
 
     async_fire_mqtt_message(
-        hass, "homeassistant/binary_sensor/bla/config", '{ "name": "Beer" }'
+        hass,
+        "homeassistant/binary_sensor/bla/config",
+        '{ "name": "Beer", "state_topic": "test-topic" }',
     )
     await hass.async_block_till_done()
     async_fire_mqtt_message(hass, "homeassistant/binary_sensor/bla/config", "")
@@ -431,93 +447,6 @@ async def test_missing_discover_abbreviations(hass, mqtt_mock, caplog):
     assert not missing
 
 
-async def test_implicit_state_topic_alarm(hass, mqtt_mock, caplog):
-    """Test implicit state topic for alarm_control_panel."""
-    entry = MockConfigEntry(domain=mqtt.DOMAIN)
-
-    await async_start(hass, "homeassistant", {}, entry)
-
-    data = (
-        '{ "name": "Test1",'
-        '  "command_topic": "homeassistant/alarm_control_panel/bla/cmnd"'
-        "}"
-    )
-
-    async_fire_mqtt_message(hass, "homeassistant/alarm_control_panel/bla/config", data)
-    await hass.async_block_till_done()
-    assert (
-        "implicit state_topic is deprecated, add "
-        '"state_topic":"homeassistant/alarm_control_panel/bla/state"' in caplog.text
-    )
-
-    state = hass.states.get("alarm_control_panel.Test1")
-    assert state is not None
-    assert state.name == "Test1"
-    assert ("alarm_control_panel", "bla") in hass.data[ALREADY_DISCOVERED]
-    assert state.state == "unknown"
-
-    async_fire_mqtt_message(
-        hass, "homeassistant/alarm_control_panel/bla/state", "armed_away"
-    )
-
-    state = hass.states.get("alarm_control_panel.Test1")
-    assert state.state == "armed_away"
-
-
-async def test_implicit_state_topic_binary_sensor(hass, mqtt_mock, caplog):
-    """Test implicit state topic for binary_sensor."""
-    entry = MockConfigEntry(domain=mqtt.DOMAIN)
-
-    await async_start(hass, "homeassistant", {}, entry)
-
-    data = '{ "name": "Test1"' "}"
-
-    async_fire_mqtt_message(hass, "homeassistant/binary_sensor/bla/config", data)
-    await hass.async_block_till_done()
-    assert (
-        "implicit state_topic is deprecated, add "
-        '"state_topic":"homeassistant/binary_sensor/bla/state"' in caplog.text
-    )
-
-    state = hass.states.get("binary_sensor.Test1")
-    assert state is not None
-    assert state.name == "Test1"
-    assert ("binary_sensor", "bla") in hass.data[ALREADY_DISCOVERED]
-    assert state.state == "off"
-
-    async_fire_mqtt_message(hass, "homeassistant/binary_sensor/bla/state", "ON")
-
-    state = hass.states.get("binary_sensor.Test1")
-    assert state.state == "on"
-
-
-async def test_implicit_state_topic_sensor(hass, mqtt_mock, caplog):
-    """Test implicit state topic for sensor."""
-    entry = MockConfigEntry(domain=mqtt.DOMAIN)
-
-    await async_start(hass, "homeassistant", {}, entry)
-
-    data = '{ "name": "Test1"' "}"
-
-    async_fire_mqtt_message(hass, "homeassistant/sensor/bla/config", data)
-    await hass.async_block_till_done()
-    assert (
-        "implicit state_topic is deprecated, add "
-        '"state_topic":"homeassistant/sensor/bla/state"' in caplog.text
-    )
-
-    state = hass.states.get("sensor.Test1")
-    assert state is not None
-    assert state.name == "Test1"
-    assert ("sensor", "bla") in hass.data[ALREADY_DISCOVERED]
-    assert state.state == "unknown"
-
-    async_fire_mqtt_message(hass, "homeassistant/sensor/bla/state", "1234")
-
-    state = hass.states.get("sensor.Test1")
-    assert state.state == "1234"
-
-
 async def test_no_implicit_state_topic_switch(hass, mqtt_mock, caplog):
     """Test no implicit state topic for switch."""
     entry = MockConfigEntry(domain=mqtt.DOMAIN)
@@ -552,7 +481,7 @@ async def test_complex_discovery_topic_prefix(hass, mqtt_mock, caplog):
     async_fire_mqtt_message(
         hass,
         ("my_home/homeassistant/register/binary_sensor/node1/object1/config"),
-        '{ "name": "Beer" }',
+        '{ "name": "Beer", "state_topic": "test-topic" }',
     )
     await hass.async_block_till_done()
 
diff --git a/tests/components/mqtt/test_light_json.py b/tests/components/mqtt/test_light_json.py
index 6a8bf10dc3d..c07cec47ecc 100644
--- a/tests/components/mqtt/test_light_json.py
+++ b/tests/components/mqtt/test_light_json.py
@@ -91,8 +91,7 @@ import json
 from unittest import mock
 from unittest.mock import patch
 
-from homeassistant.components import light, mqtt
-from homeassistant.components.mqtt.discovery import async_start
+from homeassistant.components import light
 from homeassistant.const import (
     ATTR_ASSUMED_STATE,
     ATTR_SUPPORTED_FEATURES,
@@ -122,7 +121,7 @@ from .common import (
     help_test_update_with_json_attrs_not_dict,
 )
 
-from tests.common import MockConfigEntry, async_fire_mqtt_message, mock_coro
+from tests.common import async_fire_mqtt_message, mock_coro
 from tests.components.light import common
 
 DEFAULT_CONFIG = {
@@ -1061,22 +1060,6 @@ async def test_discovery_removal(hass, mqtt_mock, caplog):
     await help_test_discovery_removal(hass, mqtt_mock, caplog, light.DOMAIN, data)
 
 
-async def test_discovery_deprecated(hass, mqtt_mock, caplog):
-    """Test discovery of mqtt_json light with deprecated platform option."""
-    entry = MockConfigEntry(domain=mqtt.DOMAIN)
-    await async_start(hass, "homeassistant", {"mqtt": {}}, entry)
-    data = (
-        '{ "name": "Beer",'
-        '  "platform": "mqtt_json",'
-        '  "command_topic": "test_topic"}'
-    )
-    async_fire_mqtt_message(hass, "homeassistant/light/bla/config", data)
-    await hass.async_block_till_done()
-    state = hass.states.get("light.beer")
-    assert state is not None
-    assert state.name == "Beer"
-
-
 async def test_discovery_update_light(hass, mqtt_mock, caplog):
     """Test update of discovered light."""
     data1 = (
diff --git a/tests/components/mqtt/test_light_template.py b/tests/components/mqtt/test_light_template.py
index f3965479c14..4f89ca77847 100644
--- a/tests/components/mqtt/test_light_template.py
+++ b/tests/components/mqtt/test_light_template.py
@@ -28,8 +28,7 @@ If your light doesn't support RGB feature, omit `(red|green|blue)_template`.
 """
 from unittest.mock import patch
 
-from homeassistant.components import light, mqtt
-from homeassistant.components.mqtt.discovery import async_start
+from homeassistant.components import light
 from homeassistant.const import (
     ATTR_ASSUMED_STATE,
     ATTR_SUPPORTED_FEATURES,
@@ -59,12 +58,7 @@ from .common import (
     help_test_update_with_json_attrs_not_dict,
 )
 
-from tests.common import (
-    MockConfigEntry,
-    assert_setup_component,
-    async_fire_mqtt_message,
-    mock_coro,
-)
+from tests.common import assert_setup_component, async_fire_mqtt_message, mock_coro
 from tests.components.light import common
 
 DEFAULT_CONFIG = {
@@ -883,24 +877,6 @@ async def test_discovery_removal(hass, mqtt_mock, caplog):
     await help_test_discovery_removal(hass, mqtt_mock, caplog, light.DOMAIN, data)
 
 
-async def test_discovery_deprecated(hass, mqtt_mock, caplog):
-    """Test discovery of mqtt template light with deprecated option."""
-    entry = MockConfigEntry(domain=mqtt.DOMAIN)
-    await async_start(hass, "homeassistant", {"mqtt": {}}, entry)
-    data = (
-        '{ "name": "Beer",'
-        '  "platform": "mqtt_template",'
-        '  "command_topic": "test_topic",'
-        '  "command_on_template": "on",'
-        '  "command_off_template": "off"}'
-    )
-    async_fire_mqtt_message(hass, "homeassistant/light/bla/config", data)
-    await hass.async_block_till_done()
-    state = hass.states.get("light.beer")
-    assert state is not None
-    assert state.name == "Beer"
-
-
 async def test_discovery_update_light(hass, mqtt_mock, caplog):
     """Test update of discovered light."""
     data1 = (
diff --git a/tests/components/mqtt/test_sensor.py b/tests/components/mqtt/test_sensor.py
index 5e472efcc89..0455c5f9c7c 100644
--- a/tests/components/mqtt/test_sensor.py
+++ b/tests/components/mqtt/test_sensor.py
@@ -240,98 +240,6 @@ async def test_custom_availability_payload(hass, mqtt_mock):
     )
 
 
-async def test_setting_sensor_attribute_via_legacy_mqtt_json_message(hass, mqtt_mock):
-    """Test the setting of attribute via MQTT with JSON payload."""
-    assert await async_setup_component(
-        hass,
-        sensor.DOMAIN,
-        {
-            sensor.DOMAIN: {
-                "platform": "mqtt",
-                "name": "test",
-                "state_topic": "test-topic",
-                "unit_of_measurement": "fav unit",
-                "json_attributes_topic": "test-attributes-topic",
-            }
-        },
-    )
-
-    async_fire_mqtt_message(hass, "test-attributes-topic", '{ "val": "100" }')
-    state = hass.states.get("sensor.test")
-
-    assert state.attributes.get("val") == "100"
-
-
-async def test_update_with_legacy_json_attrs_not_dict(hass, mqtt_mock, caplog):
-    """Test attributes get extracted from a JSON result."""
-    assert await async_setup_component(
-        hass,
-        sensor.DOMAIN,
-        {
-            sensor.DOMAIN: {
-                "platform": "mqtt",
-                "name": "test",
-                "state_topic": "test-topic",
-                "unit_of_measurement": "fav unit",
-                "json_attributes_topic": "test-attributes-topic",
-            }
-        },
-    )
-
-    async_fire_mqtt_message(hass, "test-attributes-topic", '[ "list", "of", "things"]')
-    state = hass.states.get("sensor.test")
-
-    assert state.attributes.get("val") is None
-    assert "JSON result was not a dictionary" in caplog.text
-
-
-async def test_update_with_legacy_json_attrs_bad_JSON(hass, mqtt_mock, caplog):
-    """Test attributes get extracted from a JSON result."""
-    assert await async_setup_component(
-        hass,
-        sensor.DOMAIN,
-        {
-            sensor.DOMAIN: {
-                "platform": "mqtt",
-                "name": "test",
-                "state_topic": "test-topic",
-                "unit_of_measurement": "fav unit",
-                "json_attributes_topic": "test-attributes-topic",
-            }
-        },
-    )
-
-    async_fire_mqtt_message(hass, "test-attributes-topic", "This is not JSON")
-
-    state = hass.states.get("sensor.test")
-    assert state.attributes.get("val") is None
-    assert "Erroneous JSON: This is not JSON" in caplog.text
-
-
-async def test_update_with_legacy_json_attrs_and_template(hass, mqtt_mock):
-    """Test attributes get extracted from a JSON result."""
-    assert await async_setup_component(
-        hass,
-        sensor.DOMAIN,
-        {
-            sensor.DOMAIN: {
-                "platform": "mqtt",
-                "name": "test",
-                "state_topic": "test-topic",
-                "unit_of_measurement": "fav unit",
-                "value_template": "{{ value_json.val }}",
-                "json_attributes": "val",
-            }
-        },
-    )
-
-    async_fire_mqtt_message(hass, "test-topic", '{ "val": "100" }')
-    state = hass.states.get("sensor.test")
-
-    assert state.attributes.get("val") == "100"
-    assert state.state == "100"
-
-
 async def test_invalid_device_class(hass, mqtt_mock):
     """Test device_class option with invalid value."""
     assert await async_setup_component(