Background: There is limited data from Africa on the effect of pre- and post-natal growth and infant feeding on later body composition. This study's aim was to investigate the effect of birth weight, exclusive breastfeeding and infant growth on adolescent body composition, using data from a Ugandan birth cohort. Methods: Data was collected prenatally from pregnant women and prospectively from their resulting live offspring. Data on body composition (fat mass index [FMI] and fat free mass index [FFMI]) was collected from 10- and 11-year olds. Linear regression was used to assess the effect of birth weight, exclusive breastfeeding and infant growth on FMI and FFMI, adjusting for confounders. Results: 177 adolescents with a median age of 10.1 years were included in analysis, with mean FMI 2.9 kg/m 2 (standard deviation (SD) 1.2), mean FFMI 12.8 kg/m 2 (SD 1.4) and mean birth weight 3.2 kg (SD 0.5). 90 (50.9%) were male and 110 (63.2%) were exclusively breastfeeding at six weeks of age. Birth weight was associated with FMI in adolescence (regression coefficient ?= 0.66 per kg increase in birth weight, 95% confidence interval (CI) (0.04, 1.29), P=0.02), while exclusive breastfeeding (?= -0.43, 95% CI (-1.06, 0.19), P=0.12), growth 0-6 months (?= 0.24 95% CI (-0.43, 0.92), P=0.48) and growth 6-12 months (?= 0.61, 95% CI (-0.23, 1.46), P=0.11) were not associated with FMI among adolescents. Birth weight (?= 0.91, 95% CI (0.17, 1.65), P=0.01) was associated with FFMI in adolescence. Exclusive breastfeeding (?= 0.17, 95% CI (-0.60, 0.94), P=0.62), growth 0-6 months (?= 0.56, 95% CI (-0.20, 1.33), P= 0.10), and growth 6-12 months (?= -0.02, 95% CI (-1.02, 0.99), P=0.97) were not associated with FFMI. Conclusions: Birth weight predicted body composition parameters in Ugandan early adolescents, however, exclusive breastfeeding at six weeks of age and growth in infancy did not.