Nutrition during the first 1000 days of life represents a window of opportunity to reduce the risk of metabolic dysfunctions later in life. Exclusive breastfeeding (EBF) and adequate introduction of solid foods are essential to promote metabolic and nutritional benefits. We evaluated the association of infant feeding practices from birth to 6 months (M) with adiposity indicators at 12 M. We performed a secondary analysis of 106 healthy term infants born from a cohort of healthy pregnant women. Type of breastfeeding (exclusive or nonexclusive), the start of complementary feeding (CF) (before (<4 M) or after (≥4 M)), and adiposity (body mass index – BMI, body mass index-for-age – BMI/A, waist circumference – WC, and waist circumference–length ratio – WLR) were evaluated at 12 M using descriptive statistics, mean differences, X2, and linear regression models. During the first 6 M, 28.3% (n = 30) of the infants received EBF. Early CF (<4 M) was present in 26.4% (n = 28) of the infants. Children who started CF < 4 M were less breastfed, received added sugars as the most frequently introduced food category, and showed higher BMI, BMI/A, WC, and WLR; those who consumed added sugars early (<4 M) had a higher WC. Starting CF < 4 M was the main factor associated with a higher WC at 12 M. Unhealthy infant feeding practices, such as lack of EBF, early CF, and early introduction of sugars, may be associated with higher adiposity at 12 M.