This study examined whether Attachment-Based Family Therapy (ABFT) was associated with decreases in maternal psychological control and increases in maternal psychological autonomy granting, and whether such changes were associated with changes in adolescents’ attachment schema and psychological symptoms. Eighteen suicidal adolescents and their mothers received 12 weeks of ABFT. Maternal psychological control and autonomy granting behaviors were observationally coded at sessions 1 and 4. Adolescents’ reports of perceived maternal care and control, attachment-related anxiety and avoidance, and depressive symptoms and suicidal ideation were collected at baseline, 6, 12 weeks (posttreatment), and 36 weeks. Results indicated that from session 1 to session 4, maternal psychological control decreased and maternal psychological autonomy granting increased. Increases in maternal autonomy granting were associated with increases in adolescents’ perceived parental care from pre to mid-treatment and decreases in attachment-related anxiety and avoidance from pre to 3 months posttreatment. Finally, decreases in adolescents’ perceived parental control during the treatment were associated with reductions in adolescents’ depressive symptoms from pretreatment to 12 weeks posttreatment. This is the first study examining the putative change mechanisms in ABFT.