diff --git a/esphome/components/modbus_controller/switch/modbus_switch.cpp b/esphome/components/modbus_controller/switch/modbus_switch.cpp
index 7bf45366c0a..f2aae201f33 100644
--- a/esphome/components/modbus_controller/switch/modbus_switch.cpp
+++ b/esphome/components/modbus_controller/switch/modbus_switch.cpp
@@ -25,8 +25,6 @@ void ModbusSwitch::setup() {
 }
 void ModbusSwitch::dump_config() { LOG_SWITCH(TAG, "Modbus Controller Switch", this); }
 
-void ModbusSwitch::set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
-
 bool ModbusSwitch::assumed_state() { return this->assumed_state_; }
 
 void ModbusSwitch::parse_and_publish(std::span<const uint8_t> data) {
diff --git a/esphome/components/modbus_controller/switch/modbus_switch.h b/esphome/components/modbus_controller/switch/modbus_switch.h
index 688a620bac1..b98543532e6 100644
--- a/esphome/components/modbus_controller/switch/modbus_switch.h
+++ b/esphome/components/modbus_controller/switch/modbus_switch.h
@@ -31,7 +31,7 @@ class ModbusSwitch final : public Component, public switch_::Switch, public Sens
   void setup() override;
   void write_state(bool state) override;
   void dump_config() override;
-  void set_assumed_state(bool assumed_state);
+  void set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
   void set_state(bool state) { this->state = state; }
   void parse_and_publish(std::span<const uint8_t> data) override;
   void set_parent(ModbusController *parent) { this->set_controller_(parent); }
diff --git a/esphome/components/template/cover/template_cover.cpp b/esphome/components/template/cover/template_cover.cpp
index 1efab9c5b86..1bf057da5b5 100644
--- a/esphome/components/template/cover/template_cover.cpp
+++ b/esphome/components/template/cover/template_cover.cpp
@@ -53,7 +53,6 @@ void TemplateCover::loop() {
   if (changed)
     this->publish_state();
 }
-void TemplateCover::set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
 float TemplateCover::get_setup_priority() const { return setup_priority::HARDWARE; }
 Trigger<> *TemplateCover::get_open_trigger() { return &this->open_trigger_; }
 Trigger<> *TemplateCover::get_close_trigger() { return &this->close_trigger_; }
diff --git a/esphome/components/template/cover/template_cover.h b/esphome/components/template/cover/template_cover.h
index e69c91bf092..d3096ba86f9 100644
--- a/esphome/components/template/cover/template_cover.h
+++ b/esphome/components/template/cover/template_cover.h
@@ -26,7 +26,7 @@ class TemplateCover final : public cover::Cover, public Component {
   Trigger<float> *get_position_trigger();
   Trigger<float> *get_tilt_trigger();
   void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
-  void set_assumed_state(bool assumed_state);
+  void set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
   void set_has_stop(bool has_stop) { this->has_stop_ = has_stop; }
   void set_has_position(bool has_position) { this->has_position_ = has_position; }
   void set_has_tilt(bool has_tilt) { this->has_tilt_ = has_tilt; }
diff --git a/esphome/components/template/switch/template_switch.cpp b/esphome/components/template/switch/template_switch.cpp
index 27134fc8b29..edd753d3d2b 100644
--- a/esphome/components/template/switch/template_switch.cpp
+++ b/esphome/components/template/switch/template_switch.cpp
@@ -53,6 +53,5 @@ void TemplateSwitch::dump_config() {
   LOG_SWITCH("", "Template Switch", this);
   ESP_LOGCONFIG(TAG, "  Optimistic: %s", YESNO(this->optimistic_));
 }
-void TemplateSwitch::set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
 
 }  // namespace esphome::template_
diff --git a/esphome/components/template/switch/template_switch.h b/esphome/components/template/switch/template_switch.h
index 9af8517f9ac..6dc073e4b37 100644
--- a/esphome/components/template/switch/template_switch.h
+++ b/esphome/components/template/switch/template_switch.h
@@ -18,7 +18,7 @@ class TemplateSwitch final : public switch_::Switch, public Component {
   Trigger<> *get_turn_on_trigger();
   Trigger<> *get_turn_off_trigger();
   void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
-  void set_assumed_state(bool assumed_state);
+  void set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
   void loop() override;
 
   float get_setup_priority() const override;
diff --git a/esphome/components/template/valve/template_valve.cpp b/esphome/components/template/valve/template_valve.cpp
index f35fdbeaf1c..50906876399 100644
--- a/esphome/components/template/valve/template_valve.cpp
+++ b/esphome/components/template/valve/template_valve.cpp
@@ -47,7 +47,6 @@ void TemplateValve::loop() {
     this->publish_state();
 }
 
-void TemplateValve::set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
 float TemplateValve::get_setup_priority() const { return setup_priority::HARDWARE; }
 
 Trigger<> *TemplateValve::get_open_trigger() { return &this->open_trigger_; }
diff --git a/esphome/components/template/valve/template_valve.h b/esphome/components/template/valve/template_valve.h
index 9c39a3624c1..504fdb2fbaf 100644
--- a/esphome/components/template/valve/template_valve.h
+++ b/esphome/components/template/valve/template_valve.h
@@ -24,7 +24,7 @@ class TemplateValve final : public valve::Valve, public Component {
   Trigger<> *get_toggle_trigger();
   Trigger<float> *get_position_trigger();
   void set_optimistic(bool optimistic) { this->optimistic_ = optimistic; }
-  void set_assumed_state(bool assumed_state);
+  void set_assumed_state(bool assumed_state) { this->assumed_state_ = assumed_state; }
   void set_has_stop(bool has_stop) { this->has_stop_ = has_stop; }
   void set_has_position(bool has_position) { this->has_position_ = has_position; }
   void set_has_toggle(bool has_toggle) { this->has_toggle_ = has_toggle; }