We performed this case-control study with 303 polycystic ovarian syndrome (PCOS) patients and 588 age-matched controls to evaluate the relation between fertility diet score and odds of PCOS. In a fully adjusted model, the top tertile of fertility diet score compared to the bottom was associated with 22% [95%CI 0.71-0.93] lower odds of PCOS (P trend = 0.012). Ratio of monounsaturated to trans fat and vegetable protein was associated with a lower odd of PCOS. Animal protein intake and glycemic load were associated with a higher odd of PCOS. Based on our results, increasing the quality of the diet according to fertility diet score can reduce the odds of PCOS.