Although security of attachment is conceptualised as a balance between infants' attachment and exploratory behaviours, parental behaviours pertaining to infant exploration have received relatively little empirical attention. Drawing from self-determination theory, this study seeks to improve the prediction of infant attachment by assessing maternal autonomy-support during infant exploration, in addition to maternal sensitivity. Seventy-one dyads participated in two home visits. Maternal sensitivity was assessed when the infants were 12 months old, whereas maternal autonomy-support and infant attachment were assessed at 15 months. The results revealed that autonomy-support explained an additional portion of the variance in attachment when maternal socioeconomic status and sensitivity were controlled. These results speak to the relevance of a theory-driven approach to examining maternal behaviours in the context of child exploration. (Contains 1 table and 1 note.)