Believers of karma believe in ethical causation where good and bad outcomes can be traced to past moral and immoral acts. Karmic belief may have important interpersonal consequences. We investigated whether American Christians expect more trustworthiness from (and are more likely to trust) interaction partners who believe in karma. We conducted an incentivized study of the trust game where interaction partners had different beliefs in karma and God. Participants expected more trustworthiness from (and were more likely to trust) karma believers. Expectations did not match actual behavior: karmic belief was not associated with actual trustworthiness. These findings suggest that people may use others’ karmic belief as a cue to predict their trustworthiness but would err when doing so.