Farmers, agronomists, and crop insurance adjusters question whether leaf defoliation damage caused by hail or other factors affects corn (Zea mays L.) forage yield the same as grain yield. Our objective was to evaluate the effects of defoliation on corn grown for forage production. In studies conducted during 3 yr at two sites in Wisconsin and one site in Pennsylvania, forage yield decreased as leaf removal increased in severity, and as time of defoliation neared silking. Forage yield response to increasing levels of defoliation was quadratic. Averaged across all environments, forage yield decreased 16% when 100% defoliation occurred at V7. Likewise 100% defoliation decreased forage yield 43, 70, and 40% at V10, R1, and R4 growth stages, respectively. Greater forage yield decreases are measured with early defoliation (V7–V10) than predicted grain yield decreases currently used by hail adjusters. This likely occurred because both increased leaf removal and decreased grain yield combine to reduce forage yield. The response to defoliation from simulated hail damage is different between corn forage and corn grain. Alternative predictive models for estimating forage yield losses should be used by insurance adjusters.