In 2015, the FDA published revised guidance that recommended a change in blood donor deferral of men who have sex with men (MSM) from an indefinite to a 12-month deferral since last sex. We assessed whether HIV incidence or associated transfusion risk increased in first-time blood donors. Donations in four major blood collection organizations were monitored for 15 months before and two years after implementation of the 12-month MSM deferral policy. HIV-positive donations were classified as recently acquired or long-term using a recent infection testing algorithm and incidence in both periods estimated. Residual transfusion-transmission risk was estimated by multiplying incidence with the infectious pre-NAT window period, estimated using a model based on infectious dose and the screening algorithm’s sensitivity. Factors associated with incident infection in each period were assessed using Poisson Regression. Overall HIV incidence in first-time donors before implementation of the 12-month MSM deferral was estimated at 2.62/105 person-years (95% CI: 1.53,3.93), and after implementation at 2.85 (95% CI: 1.96,3.93), with no statistically significant change. In male first-time donors the incidence difference was 0.93 (95% CI: -1.74,3.58). The residual risk of HIV transfusion transmission per 106 transfusions of packed red blood cell components sourced from first-time donors was estimated at 0.32 (95% CI: 0.29,0.65) before, and 0.35 (95% CI: 0.31,0.65) after implementation, with the difference not significant. Factors associated with incident infection were the same in each period. We observed no increase in HIV incidence or HIV transfusion transmission risk after implementation of a 12-month MSM deferral policy.Copyright © 2020 American Society of Hematology.