Youngkyung Moon: , Objectives: This study examined an integrated model of maternal parenting stress, social interaction, and warmth as linking mechanisms between preschooler's attachment quality at age 1 and social competence at age 6. Methods: Participants were 172 preschoolers (89 boys and 83 girls all aged 6) and their mothers recruited for the in-depth Korea Child Panel Study. Results: Attachment security at age 1 indirectly affected preschoolers' social competence at age 6, mediated by the continuity of maternal parenting stress from age 2 to 6 and the continuity of maternal social interaction and warmth from age 2 to 6. Additionally, maternal parenting stress affected maternal parenting behavior during the same period. Attachment security at age 1 did not directly affect preschoolers' social competence at age 6. Conclusion: This study showed that the parenting environment and maternal social interaction and warmth should be considered to explain the effects of attachment security during infancy on preschoolers' social competence.