Examined temporal relations between maternal mood and disruptive child behaviour using daily assessments of 30 mother-child dyads carried out over 8 consecutive weeks (623 pooled observations). Pooled time-series analyses showed synchronous fluctuation in child behaviour and maternal distress. Time-lagged models showed temporal relations between maternal and child outcomes that changed according to the type of maternal mood and child behaviour being reported. Controlling for cross-sectional relations, maternal anger and fatigue were related to previous child inattentive/impulsive/overactive behaviour (IO) and maternal confusion related to previous child oppositional/defiant behaviour (OD). However, maternal depression, low vigour, anger, and anxiety each predicted subsequent child IO and maternal confusion and anxiety each predicted subsequent child OD. Mutual influences on maternal and child functioning were interpreted in the context of interpersonal mechanisms that mediate psychological problems within families and their implications for treatment.