This longitudinal study is part of a series examining the relationships between maternal mood, feeding practices, and infant growth and development during the first 6 months of life in 226 well-nourished mother-infant dyads in Barbados. In this report, we assessed maternal moods (General Adjustment and Morale Scale and Zung Depression and Anxiety Scales), feeding practices (scales describing breast-feeding and other practices associated with infant feeding in this setting), and infant cognitive development (Griffiths Mental Development Scales). Multivariate analyses, with and without controlling for background variables, established significant relationships between maternal moods and infant cognitive development. Infants of mothers with mild–moderate depression had lower Griffiths scores than infants of mothers without depression. Maternal depressive symptoms and lack of trust at 7 weeks predicted lower infant social and performance scores at 3 months. Maternal moods at 6 months were associated with lower scores in motor development at the same age. Although no independent relationships emerged between feeding practices and infant cognitive development, the combination of diminished infant feeding intensity and maternal depression predicted delays in infant social development. These findings demonstrate the need to carefully monitor maternal moods during the postpartum period, in order to maximize the benefits of breast-feeding and related health programs to infant cognitive development.