This research was carried out to examine the impact of training in Strengthening Families Program on mental health and quality of school life of teenagers aged 10-14. This experimental study had a pretest-posttest control group design. The statistical population of the study comprised all Iranian 4^th, 5^th, and 6^th graders enrolled in school year 2018-19. The research sample which was drawn by simple random and multi-stage cluster sampling methods, consisted of 691 students (331 boys, 360 girls) and 691 parents (334 fathers, 357 mothers). The experimental groups were comprised of 387 students and 774 parents and the control groups included 304 students and 608 parents. The subjects were selected from seven provinces of Isfahan, Fars, Razavi Khorasan, Lorestan, Tehran, Tehran Counties, and Sistan and Baluchestan. Parents and adolescents received 11 training sessions (seven main sessions and four remedial sessions) in Strengthening Families Program. The research instruments included Strengthening Families Program Survey (Molgaard & Spoth, 2001), Strengths and Difficulties Questionnaire (Goodman, Meltzer, & Bailey, 2003), and Quality of School Life Questionnaire (Anderson & Bourke, 2000). Results of multivariate analysis of covariance (MANCOVA) showed that group training in SFP was effective in improving teenagers’ abilities, quality of school life, and the optimal family functions. Moreover, it reduced teenagers’ externalizing and internalizing problems. Hence, Strengthening Families Program (SFP) can be utilized to improve the psychological, social, and family health status of adolescents.