Offshore wind energy development is being pursued as a critical component in achieving a low-carbon energy economy. While the adverse effects of one wind farm on a particular wildlife population may be negligible, the aggregate effect of multiple wind farms through space and time could cause wildlife population declines. The risk of cumulative adverse effects (CAE) of offshore wind farms on wildlife is poorly researched and assessment processes are underdeveloped. Assessments of CAE must first calculate the cumulative exposure of a wildlife population to a hazard and then estimate how the exposure will affect the population. Our research responds to the first need by developing a framework to assess CAE and then developing a deterministic, geospatial decision-support model that assesses how wildlife are cumulatively exposed to the hazard of multiple wind farms. We first utilize the model to quantify how Northern Gannet (Morus bassanus) would be cumulatively exposed to three different wind farm siting scenarios along the East Coast of the U.S. The findings suggest that Northern Gannets will be cumulatively exposed regardless of siting decisions and avoidance is not an effective mitigation measure. Second, we use the model to assess how seven seabird foraging guilds would be cumulatively exposed to the same three wind farm siting scenarios. The model outputs indicate that no single offshore wind siting decision can reduce the cumulative exposure for all guilds. Based upon these findings, we identify the foraging guilds most likely to be cumulatively exposed and propose an approach for siting and mitigation that reduces cumulative exposure for all guilds.