Although studies have highlighted the role played by couple and parental relationships for children's psychosocial adjustment, especially in challenging situations, research on these two relationship domains has largely developed separately and mostly focussed on negative couple processes. However, Family Systems Theory highlights how these subsystems are interconnected, and studies inspired by this theoretical framework provide evidence of how the quality of the interparental relationship predicts the parent–child relationship. This study focussed on the association between two relational resources (dyadic coping and parent–child relationship quality) and children's emotional difficulties during the outbreak of the COVID‐19 pandemic in Italy. Five hundred ninety‐one Italian parents filled in an online self‐report questionnaire. A path analysis model was estimated to test the mediating role of parent–child relationship quality in the association between partner positive dyadic coping and children's emotional difficulties. The findings showed both a direct effect and an indirect effect of partner positive dyadic coping on children's emotional difficulties, because parent–child relationship quality partially mediated this association. Enhancing parents' ability to cope together with stress and the quality of the parent–child relationship might contribute to decrease children's vulnerability to emotional difficulties in challenging times.