Polycystic ovary syndrome (PCOS) is a common endocrine disorder that is characterized by menstrual irregularity and elevated serum androgens and is often accompanied by obesity and infertility. Aim: the study aimed to evaluate the effect of lifestyle modifications on reproductive function among infertile obese women with polycystic ovarian syndrome. Setting: the study was conducted at the outpatient gynecology and obstetrics clinic at Ain Shams University Maternity Hospital. Subjects and methods: A quasi-experimental design of one group "pre/post-test" was utilized to achieve the aim of the current study. Sample: A purposive sample included 60 infertile overweight or obese women diagnosed with PCOS. Four tools were utilized to collect data; collect data; 1) Structured interviewing questionnaire, 2) Menstrual feature assessment, 3) Reproductive hormonal essay report, and 4) Follow-up assessment tool Results: Based on a comparison between pretest and posttest related to reproductive function and BMI, data revealed that there was improvement in the menstrual disorders with statistically significant differences in menstrual irregularity, bleeding with menstruation, amenorrhea and oligomenorrhea (P= 0.004; P=0.001; P= 0.011; P= 0.05). Hormonal assessment pre/post-test indicated statistically significant differences regarding LH, FSH, and LH/FSH ratio (P= 0,053; P= 0.007; P= 0.02), with no statistically significant differences about total testosterone and estrone (P= 0.261; P=0.801). Concerning pre/post-test weight and BMI, there were highly statistically significant differences regarding weight and BMI (p= 0.001; p= 0.001). Conclusion: weight loss through lifestyle modifications has a positive effect on reproductive function regarding menstrual regularity and hormonal results. Recommendation: Adopting a healthy lifestyle and weight loss have a significant role in the improvement of reproductive function among obese infertile women with PCOS.