The present study aimed to investigate the effectiveness of Acceptance and Commitment Therapy (ACT) on the psychological well-being and perfectionism (including its various dimensions) of mothers with adolescent children. The research employed a quasi-experimental design featuring a pre-test, post-test, and a one-month follow-up with a control group. The statistical population consisted of all mothers of adolescents enrolled in schools in Shahriar County during the 2022–2023 academic year. To select the sample, Alborz Boys' Junior High School was randomly chosen from the list of regional schools. Subsequently, 30 eligible mothers were selected and randomly assigned to either the experimental or control group (n=15 per group). The experimental group participated in eight 90-minute group sessions of ACT, while the control group received no intervention. Data were collected using the Besharat Multidimensional Perfectionism Scale (2007)—based on the Hewitt and Flett (1991) theoretical model—and the Ryff’s Scale of Psychological Well-being (1989). Statistical analysis was performed using repeated measures ANOVA via SPSS version 26. The findings indicated that the treatment was effective and maintained its impact over time on psychological well-being (P < 0.05), as well as overall perfectionism and its self-oriented and other-oriented dimensions (P < 0.05). Consequently, it can be concluded that ACT is effective in promoting psychological well-being and reducing maladaptive perfectionism in mothers of adolescents, suggesting its utility in clinical and educational centers.