Contemporarily, two martial arts have emerged as highly popular among youth; Mixed Martial Arts (MMA) and Brazilian Jiu-Jiutsu (BJJ). Despite their popularity, we know little of how they affect individuals sociopsychologically. The current study sought to explore how the currently underexplored martial art disciplines may contribute to sociopsychological development among young people. In addition, it was investigated whether individuals who are predisposed to different traits may favour one sport over the other. This study was conducted with a longitudinal design; over the course of 5 months, 113 participants completed training in either condition. The results show that both groups displayed increased self-control and pro-social behaviour; however, MMA practitioners also reported increased aggressiveness, whereas BJJ practitioners experienced a decline in aggression. Accordingly, individuals who trained in MMA displayed substantially higher pre-existing aggression levels than the BJJ practitioners. The current results further corroborate research suggesting that modern martial arts and MMA may not be suitable for at-risk youth to practice, whereas traditional martial arts and sports with a healthy philosophical foundation may be effective in reducing antisocial behaviour while enhancing socially desirable behaviour among young people.