Until recently, research examining the application of Rational Emotive Behavior Therapy (REBT) in sports settings was virtually absent in South Africa. Despite the growing evidence of REBT's potential as a psychological intervention in Western nations, its use within the multicultural and sports-fervent context of South Africa remains unexplored. Moreover, limited research has addressed the impact of REBT on rugby players, with only a few case studies being reported. The current experiment employs a cluster randomized trial (CRT) to compare the effects of a 7-week preferential REBT program with a 7-week Mindfulness-Acceptance-Commitment (MAC) program on irrational beliefs, competitive anxiety and subjective performance, among adolescent South African rugby players. We also include a wait-list control group who received neither REBT nor MAC. Results indicate that athletes receiving REBT reported greater improvements in irrational beliefs, anxiety, and subjective performance, while that athletes receiving MAC also reported some improvements in anxiety. This study highlights the potential of REBT as a valuable psychological intervention in the context of South African adolescent rugby players.