Fathers’ experiences of competing demands in parenting and work domains suggest that increasing work–family conflicts are an issue for many families. Using data from the Growing Up in Australia longitudinal study, we explored this conflict and any flow‑on effects for children’s mental health. We find that parenting and relationship resources deteriorate when fathers’ work–family conflict increases or is sustained; this in turn affects children’s socio-emotional development and wellbeing.
• When fathers moved into high work–family conflict their mental health, couple relationship quality and parenting capabilities deteriorated. These adversities flowed on to negatively affect their children’s mental health.
• When fathers were able to move out of work–family conflict mental health improved for themselves and their children.
• Fathers’ work–family conflict is an important (and to date largely unrecognised) social determinant of children’s mental health, pointing at the need for policies and procedures that focus on reducing fathers’ experiences of work–family conflict.