Objective. Research on associations between parents’ personality and parenting has a long history, but mechanisms that explain them remain unsettled. We examined parents’ explicit and implicit negative Internal Working Models (IWMs) of the child, assessed at toddler age, as linking parental personality and parenting. Method. Mothers and fathers from 200 community families provided personality self-reports (Neuroticism, Agreeableness, Empathy, and Anger/Hostility) when their children were infants. When children were toddlers, the explicit negative IWMs included self-reported low-mentalizing reflective functioning and resentment regarding the child. The implicit negative IWMs were coded as negative relational schemas from parental interviews. Parental positive affect, responsiveness, and power-assertive control were observed in lengthy interactions. Measures were parallel for mother- and father-child dyads. Results. Mothers’ implicit IWMs linked the association between low Empathy and more power-assertive control. Fathers’ explicit IWMs linked the associations between high Neuroticism and low Agreeableness and lower responsiveness. Additionally, fathers’ Agreeableness and Empathy directly predicted their parenting. Two paths (Agreeableness → implicit IWMs, and explicit IWMs → responsiveness) significantly differed between mothers and fathers. Conclusions. IWMs may link parental personality with parenting. The findings integrate and inform several bodies of literature in personality, social cognition, and developmental psychology.