Objective: The aim of the present study was to investigate the role of object relations quality and personality functioning levels in predicting the tendency toward extramarital relationships among couples attending counseling clinics in Tehran. Methods and Materials: This applied, descriptive-correlational study was conducted on a statistical population comprising all couples referred to counseling clinics in 2022. Using convenience sampling, 315 questionnaires were collected, and after excluding 15 incomplete questionnaires, data from 300 participants were analyzed. The instruments included Bell’s Object Relations Inventory, Bender’s Levels of Personality Functioning Questionnaire, and the Whatley’s Attitudes Toward Infidelity Scale. Data were analyzed using multiple linear regression in SPSS version 26. Findings: Pearson correlation analysis showed significant relationships between attitudes toward extramarital relationships and object relations quality (r = 0.42, p < 0.01), as well as personality functioning levels (r = -0.38, p < 0.01). The multiple regression model was significant (F = 50.82, p < 0.01), indicating that object relations quality (β = 0.36) and personality functioning levels (β = -0.30) were both significant predictors of attitudes toward extramarital relationships, together explaining 26% of the variance. Conclusion: The findings underscore the importance of addressing object relations quality and personality functioning levels in preventive and therapeutic interventions in family counseling, suggesting that enhancing these factors can reduce the tendency toward extramarital relationships.