Identifying the impact of physicians on health outcomes is a challenging task due to the nonrandom sorting between physicians, hospitals, and patients. We overcome this challenge by exploiting a Colombian government program that randomly assigned 2,126 physicians to 618 small hospitals. We estimate the impact on the 256,806 children whose mothers received care in those hospitals during their pregnancy, using administrative data from the program, hospitals’ vital statistics records, and physicians’ records from mandatory health-specific graduation exams. We find that more-skilled physicians improve health at birth outcomes. That is, being assigned a physician with a one standard deviation higher performance in the health graduation exam scores decreases the probability of giving birth to an unhealthy baby by 6.31 percent. We present evidence that an underlying mechanism includes improving the targeting of care toward the more vulnerable mothers.