This study examined the effect of the interaction between rational/ emotional appeal types and environmental concern on consumers’ purchase intentions when delivering persuasive messages about eco-friendly products using virtual influencers. Additionally, it analyzed the mediating effects of attractiveness, trustworthiness, and expertise—key factors constituting source credibility. The study was conducted as an online experiment, utilizing AI-generated virtual influencers as stimuli. This study sought to differentiate itself from previous research by utilizing empathetic content in emotional appeals. A total of 230 participants took part in the experiment via an online platform. The analysis revealed that the interaction between appeal type and environmental concern had a significant effect on purchase intention, with rational appeals proving more effective when environmental concern was high, and emotional appeals proving more effective when environmental concern was low. Furthermore, attractiveness, trustworthiness, and expertise were found to mediate the effect of the interaction between appeal type and environmental concern on purchase intention. This study provides theoretical and practical implications for designing effective messages in eco-friendly marketing using virtual influencers, depending on the situation.