diff --git a/esphome/components/light/light_call.cpp b/esphome/components/light/light_call.cpp
index 2b13b40a16c..67fd175ce67 100644
--- a/esphome/components/light/light_call.cpp
+++ b/esphome/components/light/light_call.cpp
@@ -219,14 +219,11 @@ LightColorValues LightCall::validate_() {
     this->set_flag_(FLAG_HAS_STATE);
   }
 
-  // Make sure a turn-on makes the light visible: if the resulting brightness would be zero
-  // (e.g. restored from a brightness=0 turn-off), reset it to full brightness.
-  if (this->has_state() && this->state_ && (color_mode & ColorCapability::BRIGHTNESS)) {
-    float brightness = this->has_brightness() ? this->brightness_ : this->parent_->remote_values.get_brightness();
-    if (brightness == 0.0f) {
-      this->brightness_ = 1.0f;
-      this->set_flag_(FLAG_HAS_BRIGHTNESS);
-    }
+  // Make sure a simple (no specific brightness) turn-on makes the light visible
+  if (this->has_state() && this->state_ && (color_mode & ColorCapability::BRIGHTNESS) && !this->has_brightness() &&
+      this->parent_->remote_values.get_brightness() == 0.0f) {
+    this->brightness_ = 1.0f;
+    this->set_flag_(FLAG_HAS_BRIGHTNESS);
   }
 
   // Set color brightness to 100% if currently zero and a color is set.
diff --git a/esphome/components/light/light_state.cpp b/esphome/components/light/light_state.cpp
index bd778926d55..9d0181a05cf 100644
--- a/esphome/components/light/light_state.cpp
+++ b/esphome/components/light/light_state.cpp
@@ -71,6 +71,14 @@ void LightState::setup() {
       break;
   }
 
+  // A light coming up on boot must never end up on-but-invisible: if the resolved restore
+  // state is on but its brightness is zero (e.g. a stale/persisted value from before a
+  // forced-on restore mode, or an inverted restore flipping a dim-to-0 off state to on),
+  // reset it to full brightness.
+  if (recovered.state && recovered.brightness == 0.0f) {
+    recovered.brightness = 1.0f;
+  }
+
   call.set_color_mode_if_supported(recovered.color_mode);
   call.set_state(recovered.state);
   call.set_brightness_if_supported(recovered.brightness);
diff --git a/tests/integration/fixtures/light_effect_zero_brightness.yaml b/tests/integration/fixtures/light_effect_zero_brightness.yaml
new file mode 100644
index 00000000000..b98bed84dbc
--- /dev/null
+++ b/tests/integration/fixtures/light_effect_zero_brightness.yaml
@@ -0,0 +1,35 @@
+esphome:
+  name: light-effect-zero-bright
+host:
+api:  # Port will be automatically injected
+logger:
+  level: DEBUG
+
+output:
+  - platform: template
+    id: pulse_output
+    type: float
+    write_action:
+      - logger.log:
+          format: "PULSE_OUTPUT:%.4f"
+          args: [state]
+
+light:
+  - platform: monochromatic
+    name: "Test Pulse Light"
+    id: test_pulse_light
+    output: pulse_output
+    effects:
+      - pulse:
+          name: "Fast Pulse"
+          transition_length: 20ms
+          update_interval: 50ms
+          min_brightness: 0%
+          max_brightness: 100%
+      - strobe:
+          name: "Fast Strobe"
+          colors:
+            - state: true
+              duration: 50ms
+            - state: false
+              duration: 50ms
diff --git a/tests/integration/fixtures/light_initial_state.yaml b/tests/integration/fixtures/light_initial_state.yaml
index 2654c76aa05..052de0a4e58 100644
--- a/tests/integration/fixtures/light_initial_state.yaml
+++ b/tests/integration/fixtures/light_initial_state.yaml
@@ -21,6 +21,11 @@ output:
     type: float
     write_action:
       - lambda: ""
+  - platform: template
+    id: test_restore_and_on_output
+    type: float
+    write_action:
+      - lambda: ""
 
 light:
   - platform: rgb
@@ -37,3 +42,16 @@ light:
       red: 1.0
       green: 0.5
       blue: 0.0
+
+  - platform: monochromatic
+    name: "Test Restore And On Light"
+    id: test_restore_and_on_light
+    output: test_restore_and_on_output
+    restore_mode: RESTORE_AND_ON
+    # Simulates a stale/persisted zero brightness: RESTORE_AND_ON always forces the light
+    # on at boot regardless of the recovered state, so a leftover brightness of 0 must not
+    # leave the light on-but-invisible.
+    initial_state:
+      color_mode: BRIGHTNESS
+      state: false
+      brightness: 0%
diff --git a/tests/integration/test_light_calls.py b/tests/integration/test_light_calls.py
index a3a4103f5cd..b75e2fac62b 100644
--- a/tests/integration/test_light_calls.py
+++ b/tests/integration/test_light_calls.py
@@ -341,14 +341,14 @@ async def test_light_calls(
         assert state.state is True
         assert state.brightness == pytest.approx(1.0)
 
-        # Test 31b: An explicit turn-on with brightness 0 still resets to full
-        # brightness - a turn-on must never leave the light on-but-invisible. This
-        # is the same path the restore logic exercises (set_state(true) +
-        # set_brightness(0) from a persisted brightness=0 turn-off).
+        # Test 31b: An explicit turn-on with brightness 0 respects the explicit value and
+        # stays dark. Only a turn-on with no brightness specified (Test 31) restores
+        # visibility -- an explicit brightness request (e.g. from a light effect's dark
+        # phase) is never overridden.
         client.light_command(key=rgbcw_light.key, state=True, brightness=0.0)
         state = await wait_for_state_change(rgbcw_light.key)
         assert state.state is True
-        assert state.brightness == pytest.approx(1.0)
+        assert state.brightness == pytest.approx(0.0)
 
         # Test 32: Turning a light on when it already has nonzero brightness leaves
         # the brightness unchanged (the reset only happens when brightness is 0).
diff --git a/tests/integration/test_light_effect_zero_brightness.py b/tests/integration/test_light_effect_zero_brightness.py
new file mode 100644
index 00000000000..6c386d4229d
--- /dev/null
+++ b/tests/integration/test_light_effect_zero_brightness.py
@@ -0,0 +1,91 @@
+"""Integration test verifying light effects can dim to 0% brightness while staying on.
+
+Regression test for https://github.com/esphome/esphome/issues/17639, where PR #17103's
+"make turn-on visible" logic in LightCall::validate_() also clobbered brightness set by a
+running effect (e.g. pulse, strobe), forcing it back to 100% and breaking the dark phase
+of those effects.
+
+Effect ticks are published with `publish: false` (so Home Assistant isn't spammed with
+every frame), so the effect's actual output can't be observed via API state broadcasts.
+Instead, this test reads the output component's log lines, which are written on every
+update regardless of the publish flag.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import re
+from typing import Any
+
+from aioesphomeapi import EntityState, LightState
+import pytest
+
+from .state_utils import InitialStateHelper
+from .types import APIClientConnectedFactory, RunCompiledFunction
+
+
+@pytest.mark.asyncio
+async def test_light_effect_zero_brightness(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    """Pulse and strobe effects must be able to reach 0% brightness while the light stays on."""
+    output_pattern = re.compile(r"PULSE_OUTPUT:([\d.]+)")
+    observed: list[float] = []
+
+    def on_log_line(line: str) -> None:
+        match = output_pattern.search(line)
+        if match:
+            observed.append(float(match.group(1)))
+
+    async with (
+        run_compiled(yaml_config, line_callback=on_log_line),
+        api_client_connected() as client,
+    ):
+        entities, _ = await client.list_entities_services()
+        light = next(e for e in entities if e.object_id == "test_pulse_light")
+
+        state_futures: dict[int, asyncio.Future[LightState]] = {}
+
+        def on_state(state: EntityState) -> None:
+            if isinstance(state, LightState) and state.key in state_futures:
+                future = state_futures[state.key]
+                if not future.done():
+                    future.set_result(state)
+
+        # ESPHome sends the current state of every entity right after connecting; drain
+        # that initial burst so it can't be mistaken for the response to a command below.
+        initial_state_helper = InitialStateHelper(entities)
+        client.subscribe_states(initial_state_helper.on_state_wrapper(on_state))
+        await initial_state_helper.wait_for_initial_states()
+
+        async def send_and_wait(timeout: float = 5.0, **kwargs: Any) -> LightState:
+            """Send a light command and wait for the matching state response."""
+            state_futures[light.key] = asyncio.get_running_loop().create_future()
+            client.light_command(key=light.key, **kwargs)
+            return await asyncio.wait_for(state_futures[light.key], timeout=timeout)
+
+        # Turn the light on first so the effect starts from a known, visible state.
+        state = await send_and_wait(state=True, brightness=1.0)
+        assert state.state is True
+        assert state.brightness == pytest.approx(1.0)
+
+        for effect_name in ("Fast Pulse", "Fast Strobe"):
+            observed.clear()
+            state = await send_and_wait(effect=effect_name)
+            assert state.effect == effect_name
+            # Let several effect cycles run (update_interval/duration is 50ms in the fixture).
+            await asyncio.sleep(1.0)
+
+            assert observed, f"No output observed while running effect {effect_name!r}"
+            assert min(observed) == pytest.approx(0.0, abs=0.01), (
+                f"Effect {effect_name!r} never dimmed to 0% brightness while the light "
+                f"stayed on -- got min={min(observed):.4f} (values: {observed})"
+            )
+            assert max(observed) > 0.5, (
+                f"Effect {effect_name!r} never reached full brightness -- "
+                f"got max={max(observed):.4f}"
+            )
+
+        client.light_command(key=light.key, effect="None")
diff --git a/tests/integration/test_light_initial_state.py b/tests/integration/test_light_initial_state.py
index f1cd96dbf03..657e273fe73 100644
--- a/tests/integration/test_light_initial_state.py
+++ b/tests/integration/test_light_initial_state.py
@@ -11,6 +11,14 @@ from .state_utils import InitialStateHelper, require_entity
 from .types import APIClientConnectedFactory, RunCompiledFunction
 
 
+@pytest.fixture(autouse=True)
+def isolated_preferences(monkeypatch: pytest.MonkeyPatch, tmp_path) -> None:
+    """Keep host preferences per-test so RESTORE_AND_ON never loads a stale value left
+    behind by a previous run (host preferences otherwise persist to ~/.esphome/prefs,
+    keyed only by device name)."""
+    monkeypatch.setenv("ESPHOME_PREFDIR", str(tmp_path / "prefs"))
+
+
 @pytest.mark.asyncio
 async def test_light_initial_state(
     yaml_config: str,
@@ -36,3 +44,10 @@ async def test_light_initial_state(
         assert state.red == pytest.approx(1.0, abs=0.01)
         assert state.green == pytest.approx(0.5, abs=0.01)
         assert state.blue == pytest.approx(0.0, abs=0.01)
+
+        # Regression test: RESTORE_AND_ON always forces the light on at boot, even when
+        # the recovered/initial brightness was 0 -- it must never come up on-but-invisible.
+        restore_and_on_light = require_entity(entities, "test_restore_and_on_light")
+        restore_and_on_state = helper.initial_states[restore_and_on_light.key]
+        assert restore_and_on_state.state is True
+        assert restore_and_on_state.brightness == pytest.approx(1.0)