diff --git a/homeassistant/components/alexa/errors.py b/homeassistant/components/alexa/errors.py
index 2c5ced62403..f8e3720e160 100644
--- a/homeassistant/components/alexa/errors.py
+++ b/homeassistant/components/alexa/errors.py
@@ -90,6 +90,13 @@ class AlexaUnsupportedThermostatModeError(AlexaError):
     error_type = "UNSUPPORTED_THERMOSTAT_MODE"
 
 
+class AlexaUnsupportedThermostatTargetStateError(AlexaError):
+    """Class to represent unsupported climate target state error."""
+
+    namespace = "Alexa.ThermostatController"
+    error_type = "INVALID_TARGET_STATE"
+
+
 class AlexaTempRangeError(AlexaError):
     """Class to represent TempRange errors."""
 
diff --git a/homeassistant/components/alexa/handlers.py b/homeassistant/components/alexa/handlers.py
index 3e995e9ffe2..f99b0231e4d 100644
--- a/homeassistant/components/alexa/handlers.py
+++ b/homeassistant/components/alexa/handlers.py
@@ -73,6 +73,7 @@ from .errors import (
     AlexaSecurityPanelAuthorizationRequired,
     AlexaTempRangeError,
     AlexaUnsupportedThermostatModeError,
+    AlexaUnsupportedThermostatTargetStateError,
     AlexaVideoActionNotPermittedForContentError,
 )
 from .state_report import AlexaDirective, AlexaResponse, async_enable_proactive_mode
@@ -911,7 +912,13 @@ async def async_api_adjust_target_temp(
             }
         )
     else:
-        target_temp = float(entity.attributes[ATTR_TEMPERATURE]) + temp_delta
+        current_target_temp: str | None = entity.attributes.get(ATTR_TEMPERATURE)
+        if current_target_temp is None:
+            raise AlexaUnsupportedThermostatTargetStateError(
+                "The current target temperature is not set, "
+                "cannot adjust target temperature"
+            )
+        target_temp = float(current_target_temp) + temp_delta
 
         if target_temp < min_temp or target_temp > max_temp:
             raise AlexaTempRangeError(hass, target_temp, min_temp, max_temp)
diff --git a/tests/components/alexa/test_smart_home.py b/tests/components/alexa/test_smart_home.py
index c42ea0a0f6a..bbdf3efeb5f 100644
--- a/tests/components/alexa/test_smart_home.py
+++ b/tests/components/alexa/test_smart_home.py
@@ -2471,6 +2471,75 @@ async def test_thermostat(hass: HomeAssistant) -> None:
     assert call.data["preset_mode"] == "eco"
 
 
+async def test_no_current_target_temp_adjusting_temp(hass: HomeAssistant) -> None:
+    """Test thermostat adjusting temp with no initial target temperature."""
+    hass.config.units = US_CUSTOMARY_SYSTEM
+    device = (
+        "climate.test_thermostat",
+        "cool",
+        {
+            "temperature": None,
+            "target_temp_high": None,
+            "target_temp_low": None,
+            "current_temperature": 75.0,
+            "friendly_name": "Test Thermostat",
+            "supported_features": 1 | 2 | 4 | 128,
+            "hvac_modes": ["off", "heat", "cool", "auto", "dry", "fan_only"],
+            "preset_mode": None,
+            "preset_modes": ["eco"],
+            "min_temp": 50,
+            "max_temp": 90,
+        },
+    )
+    appliance = await discovery_test(device, hass)
+
+    assert appliance["endpointId"] == "climate#test_thermostat"
+    assert appliance["displayCategories"][0] == "THERMOSTAT"
+    assert appliance["friendlyName"] == "Test Thermostat"
+
+    capabilities = assert_endpoint_capabilities(
+        appliance,
+        "Alexa.PowerController",
+        "Alexa.ThermostatController",
+        "Alexa.TemperatureSensor",
+        "Alexa.EndpointHealth",
+        "Alexa",
+    )
+
+    properties = await reported_properties(hass, "climate#test_thermostat")
+    properties.assert_equal("Alexa.ThermostatController", "thermostatMode", "COOL")
+    properties.assert_not_has_property(
+        "Alexa.ThermostatController",
+        "targetSetpoint",
+    )
+    properties.assert_equal(
+        "Alexa.TemperatureSensor", "temperature", {"value": 75.0, "scale": "FAHRENHEIT"}
+    )
+
+    thermostat_capability = get_capability(capabilities, "Alexa.ThermostatController")
+    assert thermostat_capability is not None
+    configuration = thermostat_capability["configuration"]
+    assert configuration["supportsScheduling"] is False
+
+    supported_modes = ["OFF", "HEAT", "COOL", "AUTO", "ECO", "CUSTOM"]
+    for mode in supported_modes:
+        assert mode in configuration["supportedModes"]
+
+    # Adjust temperature where target temp is not set
+    msg = await assert_request_fails(
+        "Alexa.ThermostatController",
+        "AdjustTargetTemperature",
+        "climate#test_thermostat",
+        "climate.set_temperature",
+        hass,
+        payload={"targetSetpointDelta": {"value": -5.0, "scale": "KELVIN"}},
+    )
+    assert msg["event"]["payload"]["type"] == "INVALID_TARGET_STATE"
+    assert msg["event"]["payload"]["message"] == (
+        "The current target temperature is not set, cannot adjust target temperature"
+    )
+
+
 async def test_thermostat_dual(hass: HomeAssistant) -> None:
     """Test thermostat discovery with auto mode, with upper and lower target temperatures."""
     hass.config.units = US_CUSTOMARY_SYSTEM