Objectives: Considerable evidence suggests maternal psychopathology influences that of their offspring. The probability of a reverse causal pathway has been only rarely considered but is a concern, given around 10% of children manifest mental impairment during their early years. This study determines the extent to which child behavior problems at ages 5 and 14 years are associated with mothers' mental health at 21 years post birth. Study design: Longitudinal study. Methods: Data were taken from a sample of 3650 women from Mater and University of Queensland Study of Pregnancy birth cohort. Women's mental health was measured using the Mental Disorder Screening Tool at 21 years post birth. The Child Behavior Check List was used to measure internalizing, combined social/attention/thought disorder, and aggression at the age of 5 and 14 years. Logistic regression was used to derive odds ratios and 95% confidence intervals. A number of confounders were used to test for independence. Results: Following all adjustments, child internalizing behaviors and combined social/ attention/thought disorder at 5 years, and all measures of child behavior problem at 14 years were associated with mothers meeting criteria for mental health impairment at 21 years post birth. Moreover mothers of children with behavior problems at 14 years were approximately 2e3 times more likely to these meet these criteria. Conclusions: Mothers of children with behavior problems at 5 and 14 years of age were more likely to have mental health impairment at 21 years post birth. Child health professionals should be cognizant of the motherechild relationship having mutual mental health vulnerability. (C) 2017 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.