To promote pro-environmental behavior (PEB), this study specifically assessed the feeling of a desire to make oneself look better, or to be concerned about one's own “reputation” when observed by an interactive virtual agent. For this study, a controlled experiment was conducted with an interactive agent and a non-interactive agent as experiment conditions to test whether interaction with an agent promotes concern about reputation and PEB. Specifically, this study was conducted to evaluate the following two hypotheses. (Hypothesis 1): A person tends to be more concerned about their own personal reputation when contacting an interactive agent as an observer than when contacting a non-interactive agent. (Hypothesis 2): A person is more likely to perform PEB when contacting an interactive agent than when contacting a non-interactive agent. Before contacting agents, experiment participants were assessed to ascertain their degree of PEB. After interacting with either agent for 5 min, the degree of PEB performed was measured again. The improvement was then evaluated. Then, a questionnaire was administered to assess reputational concern. The questionnaire results supported Hypotheses 1 and 2 (p < .01) and clarified that agent interaction induces concern for reputation in the judgment of an agent: even a non-human agent. Results also demonstrated the importance of interaction for PEB promotion.