© 2020 Informa UK Limited, trading as Taylor & Francis Group.This study aims to examine the role of ischaemic-modified albumin (IMA) in predicting clomiphene citrate (CC) resistance in patients with CC-resistant and CC-sensitive infertile polycystic ovary syndrome (PCOS). Sixty women patients admitted to the infertility clinic were evaluated. The patients were divided into two groups. Group 1 comprised 30 infertile PCOS patients with CC resistance; group 2 was the control group comprising 30 infertile PCOS patients with CC sensitivity. Serum IMA levels of PCOS patients with CC resistance were significantly higher than CC sensitivity patients (p <.001). The independent variables BMI and age effects were adjusted according to the logistic regression method with groups. Significant differences were observed between the two groups in the levels of IMA (p =.0005), HOMA-IR (p =.0045), insulin (p =.022), free testosterone (p =.0001) and total testosterone (p =.03) values. By using ROC curve analysis for IMA between study and control groups, cut off point of IMA was calculated as 0.505 U/mL, sensitivity was 80% and specificity was 63%. The area under the curve was 0.926. This shows us that more oxidative stress (OS) occurs in the CC-resistant group. As a reflection of OS in the follicular endocrine, microenvironment may be linked with impaired oocyte developmental competence and embryo quality in association with increased IMA, free testosterone, total testosterone, insulin and HOMA-IR levels.Impact statementWhat is already known on this subject? In previous studies, IMA was compared between PCOS and control groups. In this study, serum IMA levels were measured in infertile PCOS patients resistant to CC for the first time. What the results of this study add? Serum IMA levels were significantly higher in resistant infertile PCOS patients compared to the control group. This shows us that more OS occurs in the CC-resistant group. What the implications are of these findings for clinical practice and/or further research? IMA will be a guide for PCOS management in patients with CC-resistant PCOS.