diff --git a/homeassistant/components/nest/climate_sdm.py b/homeassistant/components/nest/climate_sdm.py
index 6413b2e0dfe..b0c64329ffd 100644
--- a/homeassistant/components/nest/climate_sdm.py
+++ b/homeassistant/components/nest/climate_sdm.py
@@ -75,6 +75,8 @@ FAN_MODE_MAP = {
 }
 FAN_INV_MODE_MAP = {v: k for k, v in FAN_MODE_MAP.items()}
 
+MAX_FAN_DURATION = 43200  # 15 hours is the max in the SDM API
+
 
 async def async_setup_sdm_entry(
     hass: HomeAssistantType, entry: ConfigEntry, async_add_entities
@@ -322,4 +324,7 @@ class ThermostatEntity(ClimateEntity):
         if fan_mode not in self.fan_modes:
             raise ValueError(f"Unsupported fan_mode '{fan_mode}'")
         trait = self._device.traits[FanTrait.NAME]
-        await trait.set_timer(FAN_INV_MODE_MAP[fan_mode])
+        duration = None
+        if fan_mode != FAN_OFF:
+            duration = MAX_FAN_DURATION
+        await trait.set_timer(FAN_INV_MODE_MAP[fan_mode], duration=duration)
diff --git a/tests/components/nest/climate_sdm_test.py b/tests/components/nest/climate_sdm_test.py
index ef332d0e848..888227b9cde 100644
--- a/tests/components/nest/climate_sdm_test.py
+++ b/tests/components/nest/climate_sdm_test.py
@@ -819,6 +819,20 @@ async def test_thermostat_set_fan(hass, auth):
         "params": {"timerMode": "OFF"},
     }
 
+    # Turn on fan mode
+    await common.async_set_fan_mode(hass, FAN_ON)
+    await hass.async_block_till_done()
+
+    assert auth.method == "post"
+    assert auth.url == "some-device-id:executeCommand"
+    assert auth.json == {
+        "command": "sdm.devices.commands.Fan.SetTimer",
+        "params": {
+            "duration": "43200s",
+            "timerMode": "ON",
+        },
+    }
+
 
 async def test_thermostat_fan_empty(hass):
     """Test a fan trait with an empty response."""
@@ -938,7 +952,7 @@ async def test_thermostat_set_hvac_fan_only(hass, auth):
     assert url == "some-device-id:executeCommand"
     assert json == {
         "command": "sdm.devices.commands.Fan.SetTimer",
-        "params": {"timerMode": "ON"},
+        "params": {"duration": "43200s", "timerMode": "ON"},
     }
     (method, url, json, headers) = auth.captured_requests.pop(0)
     assert method == "post"