Abstract Background: Attachment relationship provides a secure base for the infants from which to explore the environment and a safe haven to return to in times of danger. Attachment style shapes the behavior of individuals in adulthood. There are many different measures of attachment and a lot of controversy about what they measure and how they relate to each other. Hence, we tried to evaluate the psychometric properties of one of such questionnaires on a sample of the Iranian population. Methods: “Attachment style questionnaire” designed by Van Oudenhoven measures four dimensions: secure, preoccupied, fearful and dismissing. Psychometric properties of the questionnaire were evaluated in a cross sectional study on 730 adults in Isfahan, Iran. Statistical analysis of data was performed by the explanatory factor analysis with the principal component method, Cronbach’s alpha, Pearson correlation coefficients, and the multiple analysis of variance (MANCOVA). Results: The Cronbach’s alpha for all items was 0.704. As a whole, the internal consistency was good. There was a high inter-scale correlation between preoccupied and fearful, also the secure style correlated negatively with fearful and preoccupied. The stability coefficient of the attachment scales were 0.625, 0.685, 0.777 and 0.605 for secure, fearful, preoccupied and dismissing styles respectively (P<0.001). Regarding construct validity, factor analysis showed that some items require iterations to fit the Iranian population. Conclusion: This study showed that the Persian version of ASQ has a reasonable reliability and validity in general and the questionnaire is appropriate for use among the Iranian population in future studies.