diff --git a/supervisor/addons/model.py b/supervisor/addons/model.py
index 0419d95c8..c6ca928da 100644
--- a/supervisor/addons/model.py
+++ b/supervisor/addons/model.py
@@ -13,7 +13,6 @@ from awesomeversion import AwesomeVersion, AwesomeVersionException
 
 from ..const import (
     ARCH_DEPRECATED,
-    ATTR_ADVANCED,
     ATTR_APPARMOR,
     ATTR_ARCH,
     ATTR_AUDIO,
@@ -255,8 +254,10 @@ class AddonModel(JobGroup, ABC):
 
     @property
     def advanced(self) -> bool:
-        """Return advanced mode of add-on."""
-        return self.data[ATTR_ADVANCED]
+        """Return False; advanced mode is deprecated and no longer supported."""
+        # Deprecated since Supervisor 2026.03.0; always returns False and can be
+        # removed once that version is the minimum supported.
+        return False
 
     @property
     def stage(self) -> AddonStage:
diff --git a/supervisor/addons/validate.py b/supervisor/addons/validate.py
index 6a8e84b50..2f8a2a1de 100644
--- a/supervisor/addons/validate.py
+++ b/supervisor/addons/validate.py
@@ -192,6 +192,15 @@ def _warn_addon_config(config: dict[str, Any]):
     if not name:
         raise vol.Invalid("Invalid Add-on config!")
 
+    if ATTR_ADVANCED in config:
+        # Deprecated since Supervisor 2026.03.0; this field is ignored and the
+        # warning can be removed once that version is the minimum supported.
+        _LOGGER.warning(
+            "Add-on '%s' uses deprecated 'advanced' field in config. "
+            "This field is ignored by the Supervisor. Please report this to the maintainer.",
+            name,
+        )
+
     if config.get(ATTR_FULL_ACCESS, False) and (
         config.get(ATTR_DEVICES)
         or config.get(ATTR_UART)
diff --git a/supervisor/api/addons.py b/supervisor/api/addons.py
index 9114c0f30..5fdb58e8b 100644
--- a/supervisor/api/addons.py
+++ b/supervisor/api/addons.py
@@ -187,7 +187,7 @@ class APIAddons(CoreSysAttributes):
                 ATTR_NAME: addon.name,
                 ATTR_SLUG: addon.slug,
                 ATTR_DESCRIPTON: addon.description,
-                ATTR_ADVANCED: addon.advanced,
+                ATTR_ADVANCED: addon.advanced,  # Deprecated 2026.03
                 ATTR_STAGE: addon.stage,
                 ATTR_VERSION: addon.version,
                 ATTR_VERSION_LATEST: addon.latest_version,
@@ -224,7 +224,7 @@ class APIAddons(CoreSysAttributes):
             ATTR_DNS: addon.dns,
             ATTR_DESCRIPTON: addon.description,
             ATTR_LONG_DESCRIPTION: await addon.long_description(),
-            ATTR_ADVANCED: addon.advanced,
+            ATTR_ADVANCED: addon.advanced,  # Deprecated 2026.03
             ATTR_STAGE: addon.stage,
             ATTR_REPOSITORY: addon.repository,
             ATTR_VERSION_LATEST: addon.latest_version,
diff --git a/tests/addons/test_addon.py b/tests/addons/test_addon.py
index 020740cd0..d383e5685 100644
--- a/tests/addons/test_addon.py
+++ b/tests/addons/test_addon.py
@@ -18,7 +18,7 @@ from supervisor.addons.addon import Addon
 from supervisor.addons.const import AddonBackupMode
 from supervisor.addons.model import AddonModel
 from supervisor.config import CoreConfig
-from supervisor.const import AddonBoot, AddonState, BusEvent
+from supervisor.const import ATTR_ADVANCED, AddonBoot, AddonState, BusEvent
 from supervisor.coresys import CoreSys
 from supervisor.docker.addon import DockerAddon
 from supervisor.docker.const import ContainerState
@@ -834,6 +834,14 @@ def test_auto_update_available(install_addon_example: Addon):
         assert install_addon_example.auto_update_available is False
 
 
+@pytest.mark.usefixtures("coresys")
+def test_advanced_flag_ignored(install_addon_example: Addon):
+    """Ensure advanced flag in config is ignored."""
+    install_addon_example.data[ATTR_ADVANCED] = True
+
+    assert install_addon_example.advanced is False
+
+
 async def test_paths_cache(coresys: CoreSys, install_addon_ssh: Addon):
     """Test cache for key paths that may or may not exist."""
     assert not install_addon_ssh.with_logo
diff --git a/tests/addons/test_config.py b/tests/addons/test_config.py
index f55666f8b..2385b66c4 100644
--- a/tests/addons/test_config.py
+++ b/tests/addons/test_config.py
@@ -223,6 +223,16 @@ def test_warn_legacy_machine_values(caplog: pytest.LogCaptureFixture):
     assert "Add-on config 'machine' uses deprecated values" in caplog.text
 
 
+def test_warn_advanced_deprecated(caplog: pytest.LogCaptureFixture):
+    """Warn when deprecated advanced field is present."""
+    config = load_json_fixture("basic-addon-config.json")
+    config["advanced"] = True
+
+    vd.SCHEMA_ADDON_CONFIG(config)
+
+    assert "uses deprecated 'advanced' field in config" in caplog.text
+
+
 async def test_valid_manifest_build():
     """Validate build config with manifest build from."""
     config = load_json_fixture("build-config-manifest.json")