This study examined the longitudinal relations of mother-child affect exchanges at 18?months with children's mastery motivation at 39?months. Observation and questionnaire data were collected from mother-child dyads when children were 18?months; 43 mothers again rated their children's mastery motivation at 39?months. Results suggested that after controlling for gender and the corresponding 18-month mastery aspect, positive affect exchanges had long-term positive relationships with children's persistence and competence, whereas dismissed affect exchanges had long-term negative relationships with children's persistence and independent mastery. Findings suggest that children's autonomous mastery-oriented endeavours have deep roots in their early mother-child affective interactions.