Past research has associated materialism with lower well-being. However, research on the effect of materialism on interpersonal trust and its underlying mechanism is limited. This research investigated how dispositional and situational materialism relate to interpersonal trust, as well as the mediation mechanism proposed based on a social projection account (social projection is a self-referential heuristic in which individuals assume others share similar mental experiences with them). Study 1 explored the associations of dispositional materialism with generalized and particularistic trust. The results showed that dispositional materialism could negatively predict generalized trust and particularistic trust in weak ties but could not predict particularistic trust in strong ties, and trustworthiness mediated the significant associations, aligning with the social projection principle. Study 2 examined the link between dispositional materialism and trust behavior in the trust game. The results showed that dispositional materialism negatively predicted trust behavior through the chain mediation effect of trustworthiness and social expectations about others’ trustworthiness, supporting our predictions based on the social projection account. Study 3 examined the causal relationship between materialism and interpersonal trust by activating participants’ materialistic orientation via situational cues (situational materialism). The results showed that situational materialism caused lower trust behavior, trustworthiness, and social expectations; however, situational materialism could not evoke the chain mediation effect proposed based on the social projection account. Our findings partially support the explanation of materialism-trust relation based on social projection and provide implications for trust promotion practice in the future.