Background: Polycystic ovary syndrome (PCOS) is one of the common endocrinopathies of women in the reproductive age group. Thyroid hormones have various effects on the reproductive system of female. PCOS and thyroid dysfunction are linked to each other since several years. Objective: To evaluate and detect the thyroid dysfunction in patients with PCOS attending in a tertiary care hospital in Bangladesh. Methodology: This was a prospective cross sectional study conducted from November 2018 to October 2019 at Department of Obstetrics and Gynecology in Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh on one hundred and fifty (150) PCOS women of reproductive age (15 - 45 years). All data of the study subjects regarding socio-demographic, anthropometric and clinical manifestations were recorded accordingly. Their thyroid function tests (serum level of FT3, FT4, TSH) were done at the hospital laboratory and results were recorded. Result: Mean (±SD) age of the study subjects was 24.57 ± 4.27 years. The maximum numbers [108 (72.0%)] of PCOS women were between 18 - 25 years age group. Among total (150) study population, 51 (34.0%) were overweight, 36 (24.0%) were obese and 63 (42.0%) were within normal weight level. Hirsutism was found in 87 (58%) study subjects while 24 (16%) subjects had acne in their face, 54 (36%) subjects had oligomenorrhea and 45 (30%) subjects had irregular periods. Among 150 PCOS women, 120 (80%) were married and 30 (20%) were single;of them primary infertility was detected in 58 (48.33%) women followed by the normal fertility status [51 (42.5%)] and 11 (9.17%) had secondary infertility. Among total (150) study subjects, 105 (70%) were in euthyroid state, hypothyroidism was found in 33 (22.0%) subjects and hyperthyroidism was detected in 12 (8%) subjects. Conclusions: Present study demonstrated that, thyroid disorders are prevalent in 30.0% of PCOS patients. Hypothyroidism is almost three-fold more prevalent than hyperthyroidism.