The purpose of this study was to explore how adolescent attachment to mothers, fathers, and peers impacts their psychosocial adjustmet and interpersonal relationships with mothers, fathers, and peers in Taiwan. The attachment theory by John Bowlby, Mary Ainsworth, and others was used as the conceptual framework. The research on adolescent attachment, the relationships of attachment to adolescent psychosocial adjustment and interpersonal relationships also was reviewed. The research sample included 400 seventh-grade students (190 males and 210 females) from four public high schools in Nantou County, Taiwan. Based on the attachment theory, the hypothetical model for attachment in adolescence is constructed. The instruments included the Chinese Inventory of Parent and Peer Attachment, the Chinese Behavior Assessment System for Children: Self-Report of Personality (Adolescent Form), and the Chinese Assessment of Interpersonal Relations. The Linear Structural Relationship Model (LISREL) technique was employed to test the goodness-of-fit for the hypothetical model in the research. According to the result, the adolescents’ psychosocial adjustments and interpersonal relationship are statistically influenced by attachment to parents and peers. Finally, the discussion and implications of the findings were offered.