Adopting a family system perspective, this study sets out to explore the association between family configurations of mother-child and father-child attachment to better understand children’s externalizing and internalizing behaviors in toddlerhood. A total of 182 heterosexual biparental families and their children (90 boys) were recruited from the general population. Most of the fathers and mothers were Canadian-born and the personal income and education level of the parents were high in comparison to the population of the province of Quebec at large. Attachment was assessed by direct observation using the Strange Situation Procedure (SSP) in infants aged 12–18 months. Children’s internalizing and externalizing behaviors were assessed in toddlers aged 24–30 months using questionnaires completed by both parents. Results showed that infants with resistant attachment to one parent and secure attachment to the other parent have more externalizing behaviors than children with a secure attachment to both parents. Moreover, children with a disorganized attachment to both parents showed more internalizing and externalizing problems than children with a disorganized attachment with one parent and secure with the other parent. These results highlight the need of adopting a systemic family perspective to better understand the link between attachment and children’s behavior problems.