diff --git a/homeassistant/components/modbus/binary_sensor.py b/homeassistant/components/modbus/binary_sensor.py
index f65d0ad0348..50281bd2b29 100644
--- a/homeassistant/components/modbus/binary_sensor.py
+++ b/homeassistant/components/modbus/binary_sensor.py
@@ -126,7 +126,7 @@ class SlaveSensor(CoordinatorEntity, RestoreEntity, BinarySensorEntity):
     ) -> None:
         """Initialize the Modbus binary sensor."""
         idx += 1
-        self._attr_name = f"{entry[CONF_NAME]}_{idx}"
+        self._attr_name = f"{entry[CONF_NAME]} {idx}"
         self._attr_device_class = entry.get(CONF_DEVICE_CLASS)
         self._attr_available = False
         self._result_inx = int(idx / 8)
diff --git a/tests/components/modbus/conftest.py b/tests/components/modbus/conftest.py
index 75d4d6099c9..b00f9700f7f 100644
--- a/tests/components/modbus/conftest.py
+++ b/tests/components/modbus/conftest.py
@@ -16,7 +16,7 @@ import homeassistant.util.dt as dt_util
 from tests.common import async_fire_time_changed, mock_restore_cache
 
 TEST_MODBUS_NAME = "modbusTest"
-TEST_ENTITY_NAME = "test_entity"
+TEST_ENTITY_NAME = "test entity"
 TEST_MODBUS_HOST = "modbusHost"
 TEST_PORT_TCP = 5501
 TEST_PORT_SERIAL = "usb01"
diff --git a/tests/components/modbus/test_binary_sensor.py b/tests/components/modbus/test_binary_sensor.py
index fbe0003b78a..15a03b76927 100644
--- a/tests/components/modbus/test_binary_sensor.py
+++ b/tests/components/modbus/test_binary_sensor.py
@@ -25,7 +25,7 @@ from homeassistant.core import State
 
 from .conftest import TEST_ENTITY_NAME, ReadResult, do_next_cycle
 
-ENTITY_ID = f"{SENSOR_DOMAIN}.{TEST_ENTITY_NAME}"
+ENTITY_ID = f"{SENSOR_DOMAIN}.{TEST_ENTITY_NAME}".replace(" ", "_")
 
 
 @pytest.mark.parametrize(
@@ -244,8 +244,8 @@ async def test_config_slave_binary_sensor(hass, mock_modbus):
     """Run config test for binary sensor."""
     assert SENSOR_DOMAIN in hass.config.components
 
-    for addon in ["", "_1", "_2", "_3"]:
-        entity_id = f"{SENSOR_DOMAIN}.{TEST_ENTITY_NAME}{addon}"
+    for addon in ["", " 1", " 2", " 3"]:
+        entity_id = f"{SENSOR_DOMAIN}.{TEST_ENTITY_NAME}{addon}".replace(" ", "_")
         assert hass.states.get(entity_id) is not None
 
 
@@ -315,5 +315,5 @@ async def test_slave_binary_sensor(hass, expected, slaves, mock_do_cycle):
     assert hass.states.get(ENTITY_ID).state == expected
 
     for i in range(8):
-        entity_id = f"{SENSOR_DOMAIN}.{TEST_ENTITY_NAME}_{i+1}"
+        entity_id = f"{SENSOR_DOMAIN}.{TEST_ENTITY_NAME}_{i+1}".replace(" ", "_")
         assert hass.states.get(entity_id).state == slaves[i]
diff --git a/tests/components/modbus/test_climate.py b/tests/components/modbus/test_climate.py
index db471709c10..80c8590f7cc 100644
--- a/tests/components/modbus/test_climate.py
+++ b/tests/components/modbus/test_climate.py
@@ -22,7 +22,7 @@ from homeassistant.core import State
 
 from .conftest import TEST_ENTITY_NAME, ReadResult
 
-ENTITY_ID = f"{CLIMATE_DOMAIN}.{TEST_ENTITY_NAME}"
+ENTITY_ID = f"{CLIMATE_DOMAIN}.{TEST_ENTITY_NAME}".replace(" ", "_")
 
 
 @pytest.mark.parametrize(
diff --git a/tests/components/modbus/test_cover.py b/tests/components/modbus/test_cover.py
index cc879b2c168..6797dc8713c 100644
--- a/tests/components/modbus/test_cover.py
+++ b/tests/components/modbus/test_cover.py
@@ -32,8 +32,8 @@ from homeassistant.core import State
 
 from .conftest import TEST_ENTITY_NAME, ReadResult, do_next_cycle
 
-ENTITY_ID = f"{COVER_DOMAIN}.{TEST_ENTITY_NAME}"
-ENTITY_ID2 = f"{ENTITY_ID}2"
+ENTITY_ID = f"{COVER_DOMAIN}.{TEST_ENTITY_NAME}".replace(" ", "_")
+ENTITY_ID2 = f"{ENTITY_ID}_2"
 
 
 @pytest.mark.parametrize(
@@ -270,7 +270,7 @@ async def test_restore_state_cover(hass, mock_test_state, mock_modbus):
                     CONF_SCAN_INTERVAL: 0,
                 },
                 {
-                    CONF_NAME: f"{TEST_ENTITY_NAME}2",
+                    CONF_NAME: f"{TEST_ENTITY_NAME} 2",
                     CONF_INPUT_TYPE: CALL_TYPE_COIL,
                     CONF_ADDRESS: 1235,
                     CONF_SCAN_INTERVAL: 0,
diff --git a/tests/components/modbus/test_fan.py b/tests/components/modbus/test_fan.py
index f766f816109..9b0564504d9 100644
--- a/tests/components/modbus/test_fan.py
+++ b/tests/components/modbus/test_fan.py
@@ -32,8 +32,8 @@ from homeassistant.core import State
 
 from .conftest import TEST_ENTITY_NAME, ReadResult
 
-ENTITY_ID = f"{FAN_DOMAIN}.{TEST_ENTITY_NAME}"
-ENTITY_ID2 = f"{ENTITY_ID}2"
+ENTITY_ID = f"{FAN_DOMAIN}.{TEST_ENTITY_NAME}".replace(" ", "_")
+ENTITY_ID2 = f"{ENTITY_ID}_2"
 
 
 @pytest.mark.parametrize(
@@ -228,7 +228,7 @@ async def test_restore_state_fan(hass, mock_test_state, mock_modbus):
                     CONF_SCAN_INTERVAL: 0,
                 },
                 {
-                    CONF_NAME: f"{TEST_ENTITY_NAME}2",
+                    CONF_NAME: f"{TEST_ENTITY_NAME} 2",
                     CONF_ADDRESS: 18,
                     CONF_WRITE_TYPE: CALL_TYPE_REGISTER_HOLDING,
                     CONF_SCAN_INTERVAL: 0,
diff --git a/tests/components/modbus/test_init.py b/tests/components/modbus/test_init.py
index c9beba694e8..9bd0a2caa6d 100644
--- a/tests/components/modbus/test_init.py
+++ b/tests/components/modbus/test_init.py
@@ -234,7 +234,7 @@ async def test_exception_struct_validator(do_config):
             {
                 CONF_NAME: TEST_MODBUS_NAME,
                 CONF_TYPE: TCP,
-                CONF_HOST: TEST_MODBUS_HOST + "2",
+                CONF_HOST: TEST_MODBUS_HOST + " 2",
                 CONF_PORT: TEST_PORT_TCP,
             },
         ],
@@ -246,7 +246,7 @@ async def test_exception_struct_validator(do_config):
                 CONF_PORT: TEST_PORT_TCP,
             },
             {
-                CONF_NAME: TEST_MODBUS_NAME + "2",
+                CONF_NAME: TEST_MODBUS_NAME + " 2",
                 CONF_TYPE: TCP,
                 CONF_HOST: TEST_MODBUS_HOST,
                 CONF_PORT: TEST_PORT_TCP,
@@ -296,7 +296,7 @@ async def test_duplicate_modbus_validator(do_config):
                         CONF_SLAVE: 0,
                     },
                     {
-                        CONF_NAME: TEST_ENTITY_NAME + "2",
+                        CONF_NAME: TEST_ENTITY_NAME + " 2",
                         CONF_ADDRESS: 117,
                         CONF_SLAVE: 0,
                     },
@@ -392,7 +392,7 @@ async def test_duplicate_entity_validator(do_config):
                 CONF_TYPE: TCP,
                 CONF_HOST: TEST_MODBUS_HOST,
                 CONF_PORT: TEST_PORT_TCP,
-                CONF_NAME: f"{TEST_MODBUS_NAME}2",
+                CONF_NAME: f"{TEST_MODBUS_NAME} 2",
             },
             {
                 CONF_TYPE: SERIAL,
@@ -402,7 +402,7 @@ async def test_duplicate_entity_validator(do_config):
                 CONF_PORT: TEST_PORT_SERIAL,
                 CONF_PARITY: "E",
                 CONF_STOPBITS: 1,
-                CONF_NAME: f"{TEST_MODBUS_NAME}3",
+                CONF_NAME: f"{TEST_MODBUS_NAME} 3",
             },
         ],
         {
@@ -599,7 +599,7 @@ async def test_pb_read(
     """Run test for different read."""
 
     # Check state
-    entity_id = f"{do_domain}.{TEST_ENTITY_NAME}"
+    entity_id = f"{do_domain}.{TEST_ENTITY_NAME}".replace(" ", "_")
     state = hass.states.get(entity_id).state
     assert hass.states.get(entity_id).state
 
@@ -681,7 +681,7 @@ async def test_delay(hass, mock_pymodbus):
     # We "hijiack" a binary_sensor to make a proper blackbox test.
     set_delay = 15
     set_scan_interval = 5
-    entity_id = f"{BINARY_SENSOR_DOMAIN}.{TEST_ENTITY_NAME}"
+    entity_id = f"{BINARY_SENSOR_DOMAIN}.{TEST_ENTITY_NAME}".replace(" ", "_")
     config = {
         DOMAIN: [
             {
@@ -778,7 +778,7 @@ async def test_stop_restart(hass, caplog, mock_modbus):
     """Run test for service stop."""
 
     caplog.set_level(logging.INFO)
-    entity_id = f"{SENSOR_DOMAIN}.{TEST_ENTITY_NAME}"
+    entity_id = f"{SENSOR_DOMAIN}.{TEST_ENTITY_NAME}".replace(" ", "_")
     assert hass.states.get(entity_id).state == STATE_UNKNOWN
     hass.states.async_set(entity_id, 17)
     await hass.async_block_till_done()
diff --git a/tests/components/modbus/test_light.py b/tests/components/modbus/test_light.py
index 220924733ad..f98f1105fa0 100644
--- a/tests/components/modbus/test_light.py
+++ b/tests/components/modbus/test_light.py
@@ -32,8 +32,8 @@ from homeassistant.core import State
 
 from .conftest import TEST_ENTITY_NAME, ReadResult
 
-ENTITY_ID = f"{LIGHT_DOMAIN}.{TEST_ENTITY_NAME}"
-ENTITY_ID2 = f"{ENTITY_ID}2"
+ENTITY_ID = f"{LIGHT_DOMAIN}.{TEST_ENTITY_NAME}".replace(" ", "_")
+ENTITY_ID2 = f"{ENTITY_ID}_2"
 
 
 @pytest.mark.parametrize(
@@ -228,7 +228,7 @@ async def test_restore_state_light(hass, mock_test_state, mock_modbus):
                     CONF_SCAN_INTERVAL: 0,
                 },
                 {
-                    CONF_NAME: f"{TEST_ENTITY_NAME}2",
+                    CONF_NAME: f"{TEST_ENTITY_NAME} 2",
                     CONF_ADDRESS: 18,
                     CONF_WRITE_TYPE: CALL_TYPE_REGISTER_HOLDING,
                     CONF_SCAN_INTERVAL: 0,
diff --git a/tests/components/modbus/test_sensor.py b/tests/components/modbus/test_sensor.py
index 0edd9bdc945..053dc46c6ba 100644
--- a/tests/components/modbus/test_sensor.py
+++ b/tests/components/modbus/test_sensor.py
@@ -37,7 +37,7 @@ from homeassistant.core import State
 
 from .conftest import TEST_ENTITY_NAME, ReadResult, do_next_cycle
 
-ENTITY_ID = f"{SENSOR_DOMAIN}.{TEST_ENTITY_NAME}"
+ENTITY_ID = f"{SENSOR_DOMAIN}.{TEST_ENTITY_NAME}".replace(" ", "_")
 
 
 @pytest.mark.parametrize(
diff --git a/tests/components/modbus/test_switch.py b/tests/components/modbus/test_switch.py
index 86a26e18742..006e7ee8d15 100644
--- a/tests/components/modbus/test_switch.py
+++ b/tests/components/modbus/test_switch.py
@@ -40,8 +40,8 @@ from .conftest import TEST_ENTITY_NAME, ReadResult, do_next_cycle
 
 from tests.common import async_fire_time_changed
 
-ENTITY_ID = f"{SWITCH_DOMAIN}.{TEST_ENTITY_NAME}"
-ENTITY_ID2 = f"{ENTITY_ID}2"
+ENTITY_ID = f"{SWITCH_DOMAIN}.{TEST_ENTITY_NAME}".replace(" ", "_")
+ENTITY_ID2 = f"{ENTITY_ID}_2"
 
 
 @pytest.mark.parametrize(
@@ -281,7 +281,7 @@ async def test_restore_state_switch(hass, mock_test_state, mock_modbus):
                     CONF_SCAN_INTERVAL: 0,
                 },
                 {
-                    CONF_NAME: f"{TEST_ENTITY_NAME}2",
+                    CONF_NAME: f"{TEST_ENTITY_NAME} 2",
                     CONF_ADDRESS: 18,
                     CONF_WRITE_TYPE: CALL_TYPE_REGISTER_HOLDING,
                     CONF_SCAN_INTERVAL: 0,