Using administrative records from a large national US retailer, we find that managers learn to discriminate "on the job" as they hire workers of different races. We find that idiosyncratic negative and positive experiences of managers influence the race of their future hires. Early negative experiences hiring black workers yield particularly substantial and persistent declines in the manager's subsequent black hiring. Our results highlight that individual labor market experiences of employers with minority workers systematically give rise to hiring discrimination, consistent with past experiences dynamically shaping employer perceptions of worker groups.