Adolescent motherhood is a risky situation related to poorer quality of infant caregiving. The lack of social support and increased odds for maternal depression are the main concerns. This study aimed to investigate whether maternal-foetal attachment, social support and maternal depression measured during pregnancy and after birth were associated with postpartum maternal behaviours among Brazilian adolescent mothers. Forty-one adolescent mothers participated (M[subscript age]?=?16.88 years; SD?=?1.60) in the first two waves of a longitudinal study. Both mother and infant behaviours were assessed during videotaped home observations at three months postpartum. Hierarchical regression analysis indicated that positive postpartum maternal behaviours were strongly related to concurrent, rather than prenatal, measures of social support and maternal depression. Infant birth weight was also associated with positive maternal behaviours. Findings contribute to a better understanding of the personal and contextual factors affecting maternal behaviours shortly after birth in a high-risk sample of adolescent mothers.