The present study aimed to determine the mediating role of perfectionism in the relationship between insecure attachment style and obsessive-compulsive disorder (ROCD). The present descriptive-correlational study was conducted using structural equation modeling. The statistical population of this study was married people in Lahijan in 2023; in this study, 384 people were selected using the convenience method and responded to the Frost Multidimensional Perfectionism Scale (FMPS; Frost et al., 1990), the Adult Attachment Questionnaire (AAQ; Hazan & Shaver, 1987), the Partner-Related Obsessive-Compulsive Symptoms Inventory (PROCSI; Qomian et al., 2019), and the Compulsive Compulsive Communicative Inventory (ROCI; Qomian et al., 2021). Data analysis was performed using structural equation modeling. The findings showed that the proposed model has a favorable fit. The findings showed that insecure attachment style and perfectionism had a direct effect on ROCD; insecure attachment style also had a positive and significant effect on perfectionism (P<0.05). Also, the results of the bootstrap test showed that perfectionism had a mediating role between insecure attachment style and ROCD (P<0.05). From the overall findings of this study, it can be concluded that insecure attachment had a direct effect on ROCD through the mediation of perfectionism.