SUMMARY: Pregnancy is an age-long fundamental evolutionary process through which human existence has been sustained from the days of the first man and woman and has since been from generation to generation. Pregnancy involves complex interactions between physical, cellular, endocrine and molecular events. Infertility is the inability to conceive after 1year of regular intercourse without contraception. Infertility is the most important reproductive health concern of many Nigerian women as it accounts for 60% to 70% of gynecological consultations in most tertiary health centers in Nigeria. The causes broadly include; female factors, male factor infertility, combined factors and unexplained infertility. Thyroid disorders when overt or subclinical have been shown to be common among women of reproductive age group and also in women with reproductive disorders including infertility and recurrent miscarriages. The importance of optimal thyroid functions even in patients undergoing assisted reproductive technologies (ART) cannot be over-emphasized as it also affects the outcome. Objectives: To determine the prevalence and role of subclinical thyroid dysfunction and thyroid autoimmunity among infertile women in UCH, Ibadan. Methodology: A cross-sectional study involving 302 participants. Participants consents were obtained, and detailed medical, gynecological history and examination were done. The blood samples obtained were assayed for levels of serum T4, Thyroid Stimulating Hormone (TSH) and Anti-Thyroid Peroxidase (Anti-TPO) antibodies using the enzyme linked immunosorbent assay (ELISA).