diff --git a/esphome/components/tsl2561/tsl2561.cpp b/esphome/components/tsl2561/tsl2561.cpp
index 963114b230c..5c53ed607ff 100644
--- a/esphome/components/tsl2561/tsl2561.cpp
+++ b/esphome/components/tsl2561/tsl2561.cpp
@@ -146,7 +146,6 @@ void TSL2561Sensor::set_integration_time(TSL2561IntegrationTime integration_time
   this->integration_time_ = integration_time;
 }
 void TSL2561Sensor::set_gain(TSL2561Gain gain) { this->gain_ = gain; }
-void TSL2561Sensor::set_is_cs_package(bool package_cs) { this->package_cs_ = package_cs; }
 
 bool TSL2561Sensor::tsl2561_write_byte(uint8_t a_register, uint8_t value) {
   return this->write_byte(a_register | TSL2561_COMMAND_BIT, value);
diff --git a/esphome/components/tsl2561/tsl2561.h b/esphome/components/tsl2561/tsl2561.h
index 8997d19f53a..8f6251c1342 100644
--- a/esphome/components/tsl2561/tsl2561.h
+++ b/esphome/components/tsl2561/tsl2561.h
@@ -59,7 +59,7 @@ class TSL2561Sensor final : public sensor::Sensor, public PollingComponent, publ
    *
    * @param package_cs Is this a CS package.
    */
-  void set_is_cs_package(bool package_cs);
+  void set_is_cs_package(bool package_cs) { this->package_cs_ = package_cs; }
 
   // ========== INTERNAL METHODS ==========
   // (In most use cases you won't need these)