The objectives of this developmental research were 1) to study levels and factors those influence executive functions of the brain in adolescents, 2) to study the current state and practical method for developing the training program on promoting executive functions of the brain in Adolescents (PEFs-A) and 3) to develop and study the effectiveness of the PEFs-A. The methodology consisted of three phases. Phase I was a quantitative study about the levels and the influencing factors of the executive functions of the brain in adolescents. Samples were 1200 junior high school students who were obtained by a multi-stage random sampling. An instrument was the Behavior Rating Inventory of Executive Function-Self-Report (BRIEF-SR) in Thai version. Data was analyzed by One-way Analysis of Variance. Phase II was a qualitative study based on the content analysis from an interview of 24 students and 12 teachers. Phase III was an experimental research to develop and study the effectiveness of the PEFs-A. The sample was randomized by using random assignment and matching into two groups: an experimental group and a control group, 37 students in each group. The instruments were the PEFs-A, the BRIF-SR in Thai version, and the Wisconsin Card Shorting-64 (WSCT-64). The assessments were done in 3 phases: pre-test, posttest, and follow-up. The data were analyzed by repeated measures of variance. The results revealed that 1) gender, age, academic achievement, amount of sleep, drug using, and mindfulness practice had influence effects on the executive functions of the brain with statistical significance at .05 level. 2) Almost teachers and students lacked perception and knowledge on the executive functions of the brain. Students had behaviors that indicated an executive of the brain dysfunction. In addition, they needed training to enhance their executive functions of the brain through the group training skills. 3) The PEFs-A The PEFs-A was designed by the researcher, based on integrative of acceptance and commitment therapy, neuroscience, and 12 brain/ mind learning principles. It was the training program composed of 10 sessions. Each session lasted for 50 minutes. The PEFs-A waseffective in the promotion of the executive functions of the brain with statistical significance at .05 level.