The quality of early interactions, as well as parental sensitivity to the infant’s signals, have a crucial impact on infant attachment security. The aim of this study was to examine maternal sensitivity and attachment security in a population at high psychosocial risk. Forty-six mother-infant dyads were assessed when the infants were twelve to seventeen months old. Infant attachment was assessed using the Strange Situation Paradigm (Ainsworth, et al., 1978), while maternal sensitivity was examined using the Maternal Sensitivity Scales (Ainsworth, et al., 1974) in three mother-infant filmed interaction contexts. The results revealed that maternal sensitivity is a relevant factor in the establishment of secure and insecure attachment bonds. In contrast, maternal sensitivity does not seem to be a central determinant for disorganized attachment, as the present study has found no association between these variables.