As the use of generative AI expands in advertising, it remains unclear whether the persuasive mechanisms underlying conventional nostalgia advertising operate similarly when advertisements are identified as AI-generated. This research investigated the effectiveness of nostalgia appeals and the psychological mechanism underlying their effects in generative AI advertising. Study 1 employed a field experiment using a Facebook A/B test. The results demonstrated that the AI-generated ad featuring a nostalgic (vs. control) appeal achieved higher social media engagement. Study 2 employed a 2 (ad appeal: nostalgia vs. control) × 2 (disclosed creator type: AI vs. human) between-subjects experiment. Nostalgia appeals increased brand attitude through perceived brand heritage. In addition, advertisements attributed to a human creator elicited higher perceived brand heritage and more favorable brand attitudes than those attributed to AI. However, disclosed creator type did not significantly moderate the effects of nostalgia appeals. These findings contribute to the advertising literature by identifying perceived brand heritage as a mechanism through which nostalgia appeals enhance brand attitude while providing no evidence that this process differs by disclosed creator type.