This article focuses on how maternal employment in nonstandard schedules at night, on the weekends, or that rotate on a weekly basis influence preschoolers' behavioral outcomes. Examining low-income working mothers and their children aged 2-4 years from the Welfare, Children, and Families: A Three-City Study (N = 206), we find that maternal nonstandard schedules are associated with negative behavioral outcomes for young children. There is some evidence that the negative effects of nonstandard schedules on behavior problems operate indirectly through increased parenting stress. Moderating influences of child gender and family composition are also detected. These findings are consistent with the small number of studies demonstrating the negative effects of nonstandard schedules on children of varying ages.