Middle childhood is a relative lacuna in behavioral attachment research. We examined antecedents, correlates, and implications of parent–child attachment at age 10 in a longitudinal study of community families from a Midwestern US state (N = 102, mothers, fathers, and children). Dimensions of security, avoidance, ambivalence, and disorganization of children’s attachment to each parent were observed in lengthy naturalistic interactions and assessed using Iowa Attachment Behavioral Coding (IABC). IABC scores were meaningfully associated with history of parental responsiveness (7–80 months) and with earlier and concurrent attachment security, assessed with other established instruments (parent- and observer-rated Attachment Q-Set at 25 months, children’s reports at age 8 and 10). Structural equation modeling analyses revealed that the overall history of responsive care was meaningfully associated with Security, Avoidance, and Disorganization at age 10, in both mother–child and father–child relationships, and that most recent care uniquely predicted Security. IABC scores were also meaningfully related to a broad range of measures of child adaptation at ages 10–12. Cumulative history of children’s security from infancy to middle childhood, integrating measures across relationships and methodologies, also predicted child adaptation at ages 10–12.