To examine the relationship between mothers' health-related quality of life (HRQoL) and child behaviour problems at age 2 years. To investigate whether the relationship between maternal HRQoL and child behaviour problems is independent of maternal mental health.Cross-sectional survey nested within a population-level, cluster randomised trial, which aims to prevent early child behaviour problems. One hundred and sixty mothers of 2-year-old children, in nine local government areas in Victoria, Australia. HRQoL was measured using the Assessment of Quality of Life 6D and child behaviour was measured using the child behaviour checklist (CBCL/1.5-5 years). Maternal mental health was measured using the Depression Anxiety Stress Scale. Data were collected at child age 2 years; demographic data were collected at child age 8 months.HRQoL was lower for mothers with children that had borderline/clinical behaviour problems compared to those with children without problems (mean difference -0.14, 95% confidence interval (CI): -0.16 to -0.12, P < 0.001). The finding did not markedly change when adjusting for household income, financial security, child gender, child temperament and intervention group status at child age 8 months (mean difference -0.12, 95% CI: -0.15 to -0.09, P < 0.001), but did attenuate when additionally adjusting for concurrent maternal mental health (mean difference -0.03, 95% CI: -0.05 to -0.02, P < 0.001).Child behaviour problems were associated with lower maternal HRQoL. Child behaviour problems prevention programmes could consider this association with maternal HRQoL and be designed to improve and report both mothers' and their child's health and wellbeing.