Granulosa cells produce most ovarian function indicators in infertile women like estradiol, AMH, and inhibin B. Female peptide hormone insulin-like factor 3 is produced by theca cell. Signaling of insulin-like factor 3 from theca cell stimulates antral follicle development and theca androgen production. To investigate how INSL3 levels may be a theca cell marker of ovarian reserve and the association with current markers of ovarian reserve, including AFC, FSH, E2, and AMH, in infertile women undertaking assisted reproduction. In this cross-sectional study, 75 Iraqi infertile couples were chosen at Al-Nahrain University's High Institute for Infertility Diagnosis and Assisted Reproductive Technologies from October 2022 to April 2023 for the ICSI cycle. Based on the levels of INSL3 in the serum on the day 2 of the menstrual cycle and on the day of retrieving oocyte in the follicular fluid. A comparison was made with current ovarian reserve markers (AFC, FSH, E2, and AMH) .From 75 infertile women undergoing intracytoplasmic sperm injection (ICSI), 21 of them achieved pregnancy. Positive Significant relations were found between serum INSL3 levels and anti-mullerian hormone (AMH and antral follicle count. there were no significant relationships between follicular fluids INSL3 with serum LH, FSH and E2 . The study provides compelling evidence for the significant role of INSL3 in female fertility and its association with the success of intracytoplasmic sperm injection (ICSI). Positive correlations between serum INSL3 levels and anti-mullerian hormone (AMH) and Antral follicle count AFC indicate its potential involvement in ovarian reserve and hormonal regulation.