The present study examined the association between maternal parenting stress during toddlerhood and adolescents’ later prosocial and aggressive behavior, as well as whether maternal harsh parenting in toddlerhood mediated those relations. Parenting stress has been identified as a risk factor for maladaptive parenting and children’s well-being and behavioral problems. However, few studies have considered the long-term effects of this stress in toddlerhood on outcomes in adolescence or in Latinx samples. The present sample includes 1,223 mothers and their children (48.7% girls) who identified as Latinx (55.6% Mexican-origin) from the Fragile Families and Child Wellbeing Study (FFCWS). Results showed that maternal parenting stress positively predicted adolescents’ aggressive behaviors via maternal harsh parenting. Maternal parenting stress also directly negatively predicted adolescents’ prosocial behaviors. The present study highlights the possible long-term, deleterious effects of parenting stress on parenting behaviors, and adolescents’ social behaviors.