Fathers have a unique and critical role in children’s development, but limited empirical studies have examined prenatal predictors of fathers’ parenting behaviors. Exposure to early life stressors may alter adult brain white matter fibers, especially in fibers supporting optimal cognitive and emotional functioning. As such, men with experiences of early life stressors, such as risky family environments, may enter parenthood with neurobiological differences that impact their ability to provide optimal parenting. Few studies focus on early life stressors on men’s prenatal neurobiology and subsequent parenting outcomes. This study of first-time fathers (n = 41; Mage = 31.81 years; 32% Hispanic; 32% White; 24% Asian American; 7% Black; 5% Multiracial) investigated whether risky family environments would be associated with prenatal white matter organization and postpartum parenting (infants’ Mage = 6.96 months). White matter organization was quantified through fractional anisotropy (FA), a measure of the directionality of the fibers within the tissue. Fathers reporting riskier family environments exhibited lower FA in white matter tracts like fornix and cingulum, which support connections between brain areas underlying memory and emotion regulation. Lower FA in these regions predicted less effective parenting postpartum. Findings provide insight into intergenerational transmission of family risk.