BackgroundParenting and coparenting are both important for children's adjustment, but their interaction has been little explored. Using a longitudinal design and considering two children per family, we investigated mothers' and fathers' perceptions of coparenting as moderators of associations between their coercive parenting and children's disruptive behaviour. MethodsMothers and fathers from 106 intact' families were included from the Twins, Family and Behaviour study. At Time 1 (M-child age=3years 11months, SDchild age=4.44months) parents reported on their coercive parenting and children's disruptive behaviour via questionnaire; at Time 2 (M-child age=4years 8months, SDchild age=4.44months) perceptions of coparenting and the marital relationship were collected by telephone interview. Questionnaire-based reports of children's disruptive behaviour were collected at follow-up (M-child age=5years 11months, SDchild age=5.52months). Multilevel modelling was used to examine child-specific and family-wide effects. ResultsConservative multilevel models including both maternal and paternal perceptions demonstrated that maternal perceptions of coparenting and overall coercive parenting interacted in their prediction of parent-reported child disruptive behaviour. Specifically, accounting for perceived marital quality, behavioural stability, and fathers' perceptions, only in the context of perceived higher quality coparenting was there a positive association between mother-reported overall coercive parenting and children's disruptive behaviour at follow-up. ConclusionsWhen combined with highly coercive parenting, maternal perceptions of high quality coparenting may be detrimental for children's adjustment.