Drawing on the life course paradigm, I assess how the effect of fatherhood on employment hours varies by age of becoming a parent and time elapsed since the birth. Using the National Longitudinal Survey of Youth–1979 Cohort from 1979 to 2002 (N = 28,514 observations), separate effects are estimated based on fathers’ marital status and coresidence with own children. Only unmarried men who became fathers before 24 years work longer hours immediately after a first birth, but in the long run, most early fathers work fewer hours as a result of parenthood. Over time, unmarried but coresident men who became fathers between 24 and 29 years increase their hours, as do married, coresident men who delayed fatherhood until 30 years or older. However, the latter increase is moderated by support for egalitarian gender roles. The findings shed light on the contemporary transition to adulthood and on men’s work–family balance.