Introduction: Association between hypothyroidism and infertility has been demonstrated, but its prevalence in subfertile women is not well documented. Objective: To estimate the prevalence of hypothyroidism in a cohort of subfertile women. Materials and Methods: Retrospective chart of 200 women aged 17 to 40 years with infertility attending the Reproductive Endocrine and Infertility Medicine Department between April 2008 and October 2010 was reviewed. Rate of established or newly diagnosed hypothyroidism was measured, as well as the associations between TSH > 4.2 mIU/L and patient characteristics, causes of infertility, and laboratory parameters. Results: Fourteen percent had established and 14.5% had newly diagnosed hypothyroidism. Subclinical hypothyroidism was determined for 42 (21%) women. Hypothyroidism associated significantly with both increased LH and anovulatory related infertility: LH (8.49 IU/L vs. 6.86 IU/L; p = 0.036) and anovulation in 47.8% vs. 27.3% (p = 0.009) of women with TSH > 4.2 mIU/L and TSH ≤ 4.2 mIU/L, respectively. Conclusion: This study confirms an association between hypothyroidism and infertility and highlights the need to check thyroid hormone levels prior to infertility treatment.