This study examined how the level of personalization in AI chatbot advertising (high vs. low) and the grammatical subject used to frame who is the information seeker (You vs. I) influence social presence and responses toward the chatbot (attitude toward the chatbot and intention to use). It also tested whether social presence mediates the interactive effect of personalization and grammatical subject on these responses, thereby clarifying the psychological mechanism underlying AI-based personalized advertising. The experiment revealed a significant interaction between personalization level and grammatical subject. Specifically, when the consumer was framed as the information-seeking agent (You) under high personalization, participants reported significantly higher social presence, more favorable attitudes toward the chatbot, and stronger intentions to use it than when the chatbot was framed as the agent (I). In contrast, in the chatbot-subject (I) condition, no significant differences emerged across personalization levels. Moreover, only in the consumer-subject (You) condition did social presence mediate the effect of personalization on both attitude toward the chatbot and intention to use. In other words, when consumers perceived a stronger sense of agency during the interaction, they experienced greater social presence, which in turn enhanced their attitudes toward the chatbot and their intention to use it. These findings suggest that consumer responses to AI chatbots as advertising information sources depend not only on the degree of personalization but also on consumers’ perceived sense of agency induced by grammatical subject framing.