In a randomized controlled trial 145 sexually active overweight/obese men received either a male only SHED-IT (Self Help Exercise and Diet Using IT) weight loss program or a wait-list control. Erectile function (IIEF-5) was compared between men in the active intervention versus controls. IIEF-5 was assessed at baseline, 3 months (post-intervention) and 6 months (3-month follow-up). Intention-to-treat analysis revealed a significant intervention effect for erectile function (p = 0.018) at 6 months (+1.4; 95% CI 0.3,2.4; d = 0.32). A minimal contact, gender-tailored weight loss program significantly improved men's erectile function. Further studies evaluating change in erectile function with weight loss are warranted.