Background/objectives <p>Cross-sectional studies have observed an association between obesity and vision problems. However, longitudinal studies are needed in order to understand the direction of the association.</p> Subjects/methods <p>We used de-identified data from the Growing Up in Ireland infant cohort. Analyses included 6 621 children with height, weight and Body Mass Index (BMI) measurements at age 9 and age 3 or 5. World Health Organization standards were used to classify BMI as either living with excess weight (BMI <i>≥</i> 85th percentile) or living with obesity (BMI <i>≥</i> 95th percentile). At age 9, children reported the number of minutes spent in physical exercise and in sedentary activities. Mean differences in BMI and activity times were assessed using t-tests and multiple linear regression. Differences in the incidence of gaining excess weight were assessed using multiple logistic regression after excluding children with high BMIs at age 5.</p> Results <p>The primary caregiver of 752 (11.4%) children reported that their child had a sight problem at either age 3 or 5. Average BMI increased more in these children than in children without such problems (adjusted mean difference 0.23, 95% CI 0.01,0.45). Among children who had a BMI of less than the 85th percentile at age 5, those reported to have early vision problems had 40% higher odds of having a high BMI at age 9 (OR 1.39, 95% CI 1.04, 1.85) than those without problems.</p> Conclusions <p>Children who have vision problems early in their lives are at greater risk of gaining weight.</p>