Overweight children are more prone to become overweight or obese adults. The most effective prevention is intervention in early childhood. We analyzed the association between early weight gain and overweight/obesity in 1,056 children under 11 years of age. Data were collected on lifestyle, sanitation, socioeconomic status, birth weight, and breastfeeding. Weight gain from birth until different age brackets (< 12, > 12 to 18, > 18 to 24, and > 24 to 60 months) was considered a continuous variable in z-scores. Overweight was defined as body mass index (BMI) > +1 z-score, based on 2006 and 2007 World Health Organization (WHO) guidelines. Poisson regression and linear regression were used in the multivariate statistical analysis. Weight gain rate was associated with BMI, and overweight or obesity in the 5-11-year age bracket increased twofold for each unit increase in the weight gain standard deviation between 24 and 60 months of age (RR = 2.08; 95%CI: 1.87-2.32). For all early childhood age brackets, there was an association between rapid weight gain and subsequent overweight or obesity.