Using administrative records from a large national US retailer, we find managers learn to discriminate “on the job” as they gain experience hiring workers of different races. First, we find that negative and positive experiences with black hires seed the race of future hires, consistent with managers updating their beliefs about the productivity of worker groups. Second, experiences with black workers have a larger impact on future hiring than those with white workers, consistent with greater updating about their productivity. Third, negative experiences have more persistent impacts on future hiring, consistent with negatively-biased beliefs being slower to self correct than positively-biased ones, because hiring begets learning. These dynamics, combined with the minority status of black workers, yield larger, particularly persistent declines in black hiring following managers’ negative hiring experiences. Our results suggest that managers develop biased beliefs from endogenous learning about racial groups, which systematically disadvantages minority workers.