In the last 20 years, three meta-analyses suggested that the relation between maternal sensitivity and infant attachment security was lesser in magnitude than originally believed. This led to a search for other parental behaviors likely to contribute to the development of attachment security. Based on previous theoretical propositions and empirical findings suggesting that maternal mind-mindedness may contribute to infant attachment security by favoring maternal sensitivity, the aim of this study was to examine whether sensitivity mediates the relation between maternal mind-mindedness and infant attachment security. Fifty mother-infant dyads took part in two home visits (12 months and 15 months), allowing for assessment of maternal sensitivity (T1), mind-mindedness (T1), and infant attachment (T2). The results confirmed that maternal sensitivity mediates the relation between mind-mindedness and infant attachment. The findings are discussed in light of the assessments used in this and previous studies.