Rapidly growing research on parental mind-mindedness, a tendency to treat one's young child as a psychological agent and an individual with a mind, internal mental states, and emotions, has demonstrated significant links among parents' mind-mindedness, their parenting, and multiple aspects of children's development. This prospective longitudinal study of 102 community mothers, fathers, and infants, followed from 7 months to 10 years, contributes to research on mind-mindedness by addressing several existing gaps and limitations. We examine mechanisms that account for associations between parents' early mind-mindedness and children's future attachment security, using robust behavioral measures. Teams of trained observers coded parents' mind-minded comments to their infants at 7 months during naturalistic interactions, parents' responsiveness in naturalistic interactions and in elicited imitation tasks at 15 months, and children's security, using Attachment Q-Set at 2 years and Iowa Attachment Behavioral Coding at 10 years. Sequential mediation analyses supported a model of a developmental path from parents' appropriate mind-minded comments in infancy to children's security at age 10. For mothers and children, the path was mediated first through responsiveness at 15 months and then security at 2 years. For fathers and children, the path was mediated through attachment security at 2 years. Parents' nonattuned mind-minded comments had no effects on responsiveness or security. (PsycINFO Database Record (c) 2019 APA, all rights reserved).