Examining the performance of cashiers in a French grocery store chain, we find that manager bias negatively affects minority job performance. In the stores studied, cashiers work with different managers on different days and their schedules are determined quasi-randomly. When minority cashiers, but not majority cashiers, are scheduled to work with managers who are biased (as determined by an Implicit Association Test), they are absent more often, spend less time at work, scan items more slowly, and take more time between customers. This appears to be because biased managers interact less with minorities, leading minorities to exert less effort. Manager bias has consequences for the average performance of minority workers: while on average minority and majority workers perform equivalently, on days where managers are unbiased, minorities perform significantly better than do majority workers. The findings are consistent with statistical discrimination in hiring whereby because minorities under-perform when assigned to biased managers, the firm sets a higher hiring standard for minorities to get similar average performance from minority and non-minority workers.