Abstract Introduction The progression of obesity is a continuous process involving a complex system of genetic, environmental, and behavioural factors. Socioeconomic disadvantage as well as psychological distress may lead to overeating, subsequently associated with increased energy intake and weight gain. Recent evidence indicated that the association between childhood obesity and overeating might be bidirectional. Therefore, this study aimed to longitudinally investigate the directionality of the association between childhood BMI and overeating and to identify antecedent early childhood predictors. Methods The study sample included 5,777 children from the European Longitudinal Study of Parents and Children (ELSPAC), collected between 18 months and 11 years of child age. The outcomes were child BMI and overeating. Predictors included maternal BMI, maternal education, single-parent households, financial difficulties, and adverse childhood experiences (ACEs). The random intercept cross-lagged panel model (RI-CLPM) was applied. Results The results showed temporal stability in the development of overeating and BMI, with a bidirectional relationship that strengthened over time. The child’s BMI was predicted by maternal BMI (β = 0.37, p < 0.001). The child’s overeating was predicted by maternal BMI (β = 0.13, p < 0.001), but a stronger effect was found for ACEs (β = 0.24, p < 0.001). ACEs mediated the impact of maternal education, financial difficulties, and single parenthood on overeating with indirect effects of β = -0.01 (p = 0.005), β = 0.04, (p < 0.001), and β = 0.07 (p < 0.001), respectively. Conclusions We observed stable bidirectional longitudinal effects, with a stronger association from BMI to overeating. The results suggested two main pathways: one linked to maternal BMI and early childhood BMI increase followed by overeating, and the other associated with ACEs mediating the effect of early childhood socioeconomic factors on overeating, leading to gradual BMI gain. #NGEU Key messages • The study revealed a stable bidirectional association between childhood BMI and overeating, with a stronger association from BMI to overeating. • There are two potential pathways in childhood obesity development, one involving maternal BMI, and the second associated with social disadvantage and ACEs.