Objective Vitamin D is associated with markers of ovarian reserve in women of advanced reproductive age and in vitro studies suggest that vitamin D may influence anti‐mullerian hormone (AMH). Higher vitamin D levels are also associated with improved IVF outcomes in some studies. However, less is understood regarding associations with ovarian reserve or time to pregnancy among younger women or women without a history of infertility. Our purpose was to assess the relationships between vitamin D and AMH and fecundability among women with proven fecundity. Design Secondary analysis of the EAGeR Trial, a multicenter, block‐randomized, double‐blind, placebo‐controlled clinical trial to evaluate the effect of preconception‐initiated daily low dose aspirin on reproductive outcomes in women with a history of pregnancy loss and normal fecundity. Methods Participants were attempting pregnancy, aged 18–40 years, with 1–2 prior pregnancy losses and no history of infertility. We assessed 25‐OH vitamin D and AMH in serum at baseline (not pregnant) among 1185 women. AMH levels were log‐transformed for normality. Linear regression was used to estimate associations between vitamin D and AMH concentrations adjusting for age, body mass index, race, season, physical activity, and number of prior losses. Time to hCG detected pregnancy was assessed using Cox proportional hazard regression models for discrete survival time, accounting for left truncation and right censoring, to estimate fecundability odds ratios (FOR), adjusting for the same factors. Results A total of 163 women (13.8%) had deficient vitamin D levels (