This study examined the effect of maternal employment status during the first year of a child's life on the trajectory of fathers' engagement with preschool-aged children, using the Fragile Families and Child Wellbeing Study (N = 969). Further, the role of resources was examined regarding the relationship between first-year maternal employment and the fathers' engagement trajectory, guided by the conservation of resources (COR) theory. Analyses of the growth curve models found that during children's preschool years, the engagement trajectory of fathers whose wives were employed declined more rapidly than that of fathers whose wives were not employed. When resources are held constant, the engagement trajectory of fathers whose wives were employed declined less rapidly, resulting in an increased trajectory difference. These findings emphasize the importance of trajectories of father engagement associated with maternal employment when designing intervention programmes to increase fathers' engagement with their infants.