It is important to investigate the influence of life-like agents interacting with a user since some studies suggest that life-like agents can "persuade" people, in other words, they have potential to change people's attitude and behavior. In this study, the influence of overheard communication (OC), one of famous persuasion techniques, by life-like agents toward online shopping Web site users was examined, since the OC by people often changes attitude of receivers. An experiment to compare the effect of OC by two life-like agents (a persuader agent and a persuadee agent) with regular communication by one persuader agent were conducted. The result of this experiment implied that even the OC by life-like agents could promote Web site users' online shopping purchase likelihood. Moreover, despite impression to a life-like agent as a persuader was not strongly affected by OC, attractiveness toward a persuader agent evaluated by participants was positively correlated with their purchase likelihood. These results suggest the effectiveness of the OC by life-like agents and the new direction of studies of social response to life-like agents, from the viewpoints of presence, gaze, and appearance of life-like agents.