This study investigates whether the increasingly common trend of working long hours perpetuates gender segregation in occupations. While overwork is an expected norm in many male-dominated occupations, women, especially mothers, are structurally less able to meet this expectation because their time is subject to family demands more than is men’s time. This study investigates whether the conflicting time demands of work and family increase attrition rates of mothers in male-dominated occupations, thereby reinforcing occupational segregation. Using longitudinal data drawn from the (...) Survey of Income and Program Participation, I show that mothers are more likely to leave male-dominated occupations when they work 50 hours or more per week, but the same effect is not found for men or childless women. Results also show that overworking mothers are more likely to exit the labor force entirely, and this pattern is specific to male-dominated occupations. These findings demonstrate that the norm of overwork in male-dominated workplaces and the gender beliefs operating in the family combine to reinforce gender segregation of the labor market. (shrink)