Aim of the study: To study the prevalence of vitamin D insufficiency in infertile women and see its impact as a risk factor through a case control study. This case control study was conducted at Al-Diwaniyah maternity and child teaching hospital in Al-Diwaniyah province, Mid-Euphrates region of Iraq. The study started on February 2018 and extended through February 2019. The study included 52 apparently healthy and fertile women serving as control group and 35 infertile women serving as study group. The age ranges of control and study groups were 21–39 and 20–40 years, respectively. Venous sample was obtained from each woman and sent to the central laboratory of Al-Dewaniyah maternity and child teaching hospital to measure serum vitamin D level. Mean serum vitamin D of infertile women was lower than that of fertile women, 20.57 ± 8.69 ng/ml versus 24.85 ± 5.85 ng/ml, respectively and the difference was highly significant (P = 0.007). Moreover, the prevalence rate of vitamin D insufficiency (< 20 ng/ml) was significantly higher among infertile women in comparison with fertile women, 40% versus 19.2%, respectively (P = 0.035). Vitamin D appears as a risk factor for women infertility