ABSTRACT Objective The aim of this study was to assess the serum vitamin D level in a retrospective study in women with polycystic ovary syndrome (PCOS), according to the different phenotypes of the disease. Subjects and methods In this retrospective study, the records of 351 infertile women who were diagnosed with PCOS were examined, and 200 of them were enrolled in the study randomly in 4 PCOS phenotypes. Fifty normal ovulatory women with the history of male factor were selected as the control group. Parameters, including age, infertility duration, body mass index (BMI), hormone profile, as well as the serum vitamin D level were compared among the 4 phenotypes, with the P-value ≤ 0.05 considered statistically significant. Results The findings showed a higher serum vitamin D level in the control group than in PCOS patients, which was statistically significant (P < 0.001). In addition, there was no significant difference in the serum vitamin D level among the four phenotypes of PCOS. Conclusions No significant difference was found in the serum vitamin D level of the different phenotypes of PCOS. Further studies with larger sample sizes are recommended to be done to establish the role of the serum vitamin D level in PCOS patients.