The identification of intermediate mechanisms that account for the intergenerational transmission of child maltreatment can elucidate processes of risk and resilience in families. This study investigated the role of maternal emotion dysregulation; we hypothesized that emotion dysregulation would mediate the relation between mothers’ history of maltreatment in their childhood and their aggressive behavior toward their children. Participants included 110 mothers (range = 20 to 43 years, Mage = 30.81, SDage = 6.08) with preschool-aged children (range = 3 to 5 years, Mage = 3.50, SDage = 0.51; 61% male) in a diverse community sample (46.3% African American; 50.9% had a household income under $30,000). A path analysis showed that maternal history of maltreatment in their childhood was indirectly related to later maternal psychological aggression via maternal emotion dysregulation. The indirect effect of child maltreatment on physical aggression was not statistically significant. Our findings highlight the importance of emotion regulation as a transdiagnostic risk factor for the intergenerational transmission of child maltreatment.