Key PointsQuestionIs family structure associated with the sex gap in physician earnings and hours worked?FindingsIn this cross-sectional study of 95 435 US physicians, the male-female gap in hours worked was 1% for single physicians, 7% for married physicians without children, and 18% for physicians with children. Male physicians earned 21% to 24% more per hour than female physicians across all family structures.MeaningThis study found that marriage and children were associated with a greater earnings penalty for female physicians primarily because of fewer hours worked; addressing this barrier may help to expand the effective physician workforce.