Objective: To examine the long-term effects of having one overweight or obese parent on child weight status and determine whether these effects vary according to parent sex. Design: Prospective study: Longitudinal Study of Australian Children (LSAC). Subjects: Two-parent families (N ¼ 3285) from the LSAC were included if height and weight data were available for both parents and their child at the 2004 and 2008 time points. Measurements: Child weight status category (healthy, overweight, obese) in 2008 when the child was aged 8 -9 years. Regression modelling was used to investigate how self-reported parent weight status in 2004 influenced measured child weight status 4 years later. Results: Parent body mass index (BMI) was significantly correlated with child BMI, but there was no evidence of sex-specific associations between parent and child BMI correlations. The results from the regression analysis showed that having an overweight or obese father, but a healthy weight mother, significantly increased the odds of child obesity (odds ratio: 4.18, 95% confidence interval (CI): 1.01 -17.33 and odds ratio: 14.88, 95% CI: 2.61 -84.77, respectively), but the reverse scenario (overweight or obese mother with a healthy weight father) was not a significant predictor of child overweight or obesity (odds ratio: 2.52, 95% CI: 0.38 -16.71 and odds ratio: 2.56, 95% CI: 0.31 -21.26, respectively). Conclusions: Children with overweight or obese fathers are at a higher risk of becoming obese. This suggests that interventions are urgently required to test the efficacy of treating overweight fathers as a key strategy for childhood obesity prevention and/or treatment.