diff --git a/esphome/components/ota/ota_backend.cpp b/esphome/components/ota/ota_backend.cpp
index 8fb9f67214..01a18a58ef 100644
--- a/esphome/components/ota/ota_backend.cpp
+++ b/esphome/components/ota/ota_backend.cpp
@@ -13,6 +13,19 @@ OTAGlobalCallback *get_global_ota_callback() {
   return global_ota_callback;
 }
 
+void OTAComponent::notify_state_deferred_(OTAState state, float progress, uint8_t error) {
+  // Pack state, error, and progress into a single uint32_t so the lambda
+  // captures only [this, packed] (8 bytes) — fits in std::function SBO.
+  // Layout: [state:8][error:8][progress_fixed:16] where progress is 0–10000 (0.01% resolution)
+  static_assert(OTA_ERROR <= 0xFF, "OTAState must fit in 8 bits for packing");
+  uint32_t packed = (static_cast<uint32_t>(state) << 24) | (static_cast<uint32_t>(error) << 16) |
+                    static_cast<uint16_t>(progress * 100.0f);
+  this->defer([this, packed]() {
+    this->notify_state_(static_cast<OTAState>(packed >> 24), static_cast<float>(packed & 0xFFFF) / 100.0f,
+                        static_cast<uint8_t>(packed >> 16));
+  });
+}
+
 void OTAComponent::notify_state_(OTAState state, float progress, uint8_t error) {
   for (auto *listener : this->state_listeners_) {
     listener->on_ota_state(state, progress, error);
diff --git a/esphome/components/ota/ota_backend.h b/esphome/components/ota/ota_backend.h
index 8a71135477..ab0ec58e8a 100644
--- a/esphome/components/ota/ota_backend.h
+++ b/esphome/components/ota/ota_backend.h
@@ -73,18 +73,7 @@ class OTAComponent : public Component {
    * This should be used by OTA implementations that run in separate tasks
    * (like web_server OTA) to ensure listeners execute in the main loop.
    */
-  void notify_state_deferred_(OTAState state, float progress, uint8_t error) {
-    // Pack state, error, and progress into a single uint32_t so the lambda
-    // captures only [this, packed] (8 bytes) — intended to fit in std::function SBO on supported toolchains.
-    // Layout: [state:8][error:8][progress_fixed:16] where progress is 0–10000 (0.01% resolution)
-    static_assert(OTA_ERROR <= 0xFF, "OTAState must fit in 8 bits for packing");
-    uint32_t packed = (static_cast<uint32_t>(state) << 24) | (static_cast<uint32_t>(error) << 16) |
-                      static_cast<uint16_t>(progress * 100.0f);
-    this->defer([this, packed]() {
-      this->notify_state_(static_cast<OTAState>(packed >> 24), static_cast<float>(packed & 0xFFFF) / 100.0f,
-                          static_cast<uint8_t>(packed >> 16));
-    });
-  }
+  void notify_state_deferred_(OTAState state, float progress, uint8_t error);
 
   std::vector<OTAStateListener *> state_listeners_;
 #endif