The positive impact of mental preparation on elite soccer environments has been proven by researchers and practitioners for more than a decade (Gisborne & Richardson, 2005; Nasty, 2010; Payne & Harwood, 2009). However, compared to Olympic, Paralympic, and other professional/elite environments (Durand-Bush & Salmela, 2002; Gould, Eklund, & Jackson, 1992; Jones, Hunton, & Connaughton, 2002), the use of psychology in soccer It is less accepted and used. In this regard, using mental skills in basic categories such as adult categories can have a good effect on the development of players. Researchers have emphasized the improvement of mental skills during development. However, despite the growing research and practical exercises in football academies, the practical and experimental resources available are somewhat limited. The purpose of this study was to investigate the effect of long-term mental training intervention on the mental preparation of football players under 15 years of age. The statistical population consisted of all players under 15 years of age of Tehran Persepolis football club, all 28 players voluntarily participated in this intervention. 16 sessions of 40 minutes each week at a specific time were held at the training place. The sessions included training in mental skills for the players. Before the start and after the end of the intervention, the psychological condition test was taken from the players. The research tools included the OMSAT personal information and psychological preparation questionnaire. The results of the data analysis showed that after the intervention, significant differences were seen in the scores of the constructs of visualization, concentration, recovery of concentration, relaxation, and lack of familiarity. With mental skills and long-term emphasis and review, these skills can be the reason for the growth of the scores of these structures. Structures such as commitment, self-confidence, and goal setting did not show any significant change, which could be the reason for the high scores at the beginning of the test. According to the results of the research, it is suggested to use approved psychologists to teach psychological skills to Young soccer players.