Introduction Depression is a very common disease of the present age. It is important to study the causes and factors associated with depression. The purpose of this study was to determine the correlation between perfectionism and depression of students by mediation of rumination. Methods The research method was descriptive-correlational. 270 students from Dezfoul Islamic Azad University were selected by cluster sampling. In order to collect data، "Tehran Multidimensional Perfectionism Scale” ، the “ Rumination-Reflection Scale” ، and the “ Beck Depression Inventory Second Edition” were used. Validity and reliability have been confirmed in previous studies. The model was evaluated using a structural model using the SPSS. 18 and IMOS 20. Results In structural equation model، relationships between these variables were of acceptable fit. Correlation between perfectionism and depression (β = 0. 44، P = 0. 01)، between rumination and depression (β = 0. 44، P = 0. 01)، and between perfectionism and rumination correlation of perfectionism with rumination (β = 0. 56، P = 0. 01). Conclusions Perfectionism correlates with depression either directly or indirectly through rumination. Therefore، holding workshops on improving perfectionism and managing rumination in students is recommended.