Abstract In recent years, researchers have begun to study the social consequences of conspiracy beliefs. However, little research has investigated the impact of conspiracy beliefs on interpersonal relationships. In this review, we draw attention to this issue by summarizing available empirical evidence and proposing potential social-psychological mechanisms to explain whether and why conspiracy theories affect interpersonal relationships. We firstly discuss that the attitude change that often accompanies the internalization of conspiracy beliefs might distance people’s opinions and, consequently, erode their relationships. Furthermore, we argue that the stigmatizing value of conspiracy theories can negatively affect the evaluation of conspiracy believers and discourage others from getting close to them. Finally, we consider that the misperception of social norms associated with the acceptance of certain conspiracy narratives can lead conspiracy believers to engage in non-normative behavior. Others are likely to perceive such behavior negatively, resulting in diminished interpersonal interaction. We highlight the need for further research to address these issues, as well as the potential factors that may prevent relationships being eroded by conspiracy beliefs.