Ecological contributions to attachment transmission were studied in a sample of 64 adolescent mother-infant dyads. Maternal sensitivity was assessed when infants were 6 and 10 months old, and infant security was assessed at 15 and 18 months. Maternal attachment state of mind was measured with the Adult Attachment Interview (AAI) after the 1st assessment. Ecological variables considered were maternal education and depression, paternal support, and infant maternal grandmother support. Results indicated that when the contribution of ecological variables was statistically controlled for, sensitivity was a significant mediator and state of mind no longer contributed to infant security. Sensitivity also mediated an association between maternal education and infant attachment, suggesting that attachment transmission is embedded in a more global process of infant attachment development.