Theists often receive the benefit of being stereotyped as trustworthy and moral, whereas atheists are viewed as untrustworthy and immoral. The extreme divergence between the stereotypes of theists and atheists suggests that mental images of the two groups may also diverge. We investigated whether people have biased mental images of theists and atheists. The results suggest that mental images of theists are associated with more positive attributes than images of atheists (Study 1), and these mental images influence who is believed to behave morally and immorally (Study 2). Together the findings suggest that mental images may represent a subtle mechanism reinforcing group-based prejudices.