Objectives: This study aims to (1) follow up and characterize infant growth patterns during the first year of life in Bolivia, and (2) determine whether there exists an association between weight gain and cognitive development in children living near contaminated mining industries. Methods: Data on 175 children participating to the ToxBol (Toxicity in Bolivia) birth cohort were analyzed. Rapid-growth during the first 6 months was defined as a change in weight z-score > 0.67 while slow-growth was defined as a weight z-score change of < -0.67. Neurodevelopment was evaluated using the Bayley Scales of Infant Development at 10.5-12.5 months of age. Mixed models were used to examine the association between cognitive development and weight gain. Results: Rapid growers weighed less at birth (P < 0.01). However, they revealed a higher body mass index at 12 months of age (0.70 ± 0.73, P < 0.01). After adjustment for confounding, rapid growth was not associated with cognitive development (coef = 0.49, 95% confidence interval = -4.10, 5.08). Conclusions: In this Bolivian cohort, children born smaller were more likely to grow/develop faster and attain greater weight and length. Their cognitive development was not affected by their growth patterns.