Objective: To determine what factors are associated with parental motivation to change body weight in overweight children. Design: Cross-sectional study. Setting: Dunedin, New Zealand. Subjects: Two hundred and seventy-one children aged 4-8 years, recruited in primary and secondary care, were identified as overweight (BMI ≥ 85th percentile) after screening. Parents completed questionnaires on demographics; motivation to improve diet, physical activity and weight; perception and concern about weight; parenting; and social desirability, prior to being informed that their child was overweight. Additional measures of physical activity (accelerometry), dietary intake and child behaviour (questionnaire) were obtained after feedback. Results: Although all children were overweight, only 42 % of parents perceived their child to be so, with 36 % indicating any concern. Very few parents (n 25, 8 %) were actively trying to change the child's weight. Greater motivation to change weight was observed for girls compared with boys (P = 0·001), despite no sex difference in BMI Z-score (P = 0·374). Motivation was not associated with most demographic variables, social desirability, dietary intake, parenting or child behaviour. Increased motivation to change the child's weight was observed for heavier children (P < 0·001), those who were less physically active (P = 0·002) and more sedentary (P < 0·001), and in parents who were more concerned about their child's weight (P < 0·001) or who used greater food restriction (P < 0·001). Conclusions: Low levels of parental motivation to change overweight in young children highlight the urgent need to determine how best to improve motivation to initiate change.