BACKGROUND: Core stability training (CST) is effective in improving postural balance, core endurance, and self-reported outcomes in different populations. This study aimed to investigate the effect of CST in soccer players with groin pain (GP). HYPOTHESIS: CST would improve postural balance performance, core endurance, and self-reported outcomes in soccer players with GP. STUDY DESIGN: Randomized controlled trial. LEVEL OF EVIDENCE: Level 2. METHODS: Soccer players with GP who met the selection criteria were assigned randomly to a CST (CSTG, n = 10) or a control (CG, n = 10) group. The CG undertook no additional physical activity program besides their usual training. The CSTG performed a 12-week CST comprising 76 ~75 min sessions. Static (force platform) and dynamic (Y-Balance test) postural balance, core endurance (McGill trunk endurance tests), and self-reported outcomes (Copenhagen Hip and Groin Outcome Score [HAGOS]) were assessed before and immediately after the 12-week CST. RESULTS: Significant improvements were seen in dynamic postural balance ( = 0.04 to <0.01), HAGOS scores ( = 0.02 to <0.01), and core endurance measures ( < 0.01) in the CSTG in posttest compared with pretest session and compared with CG. Static bipedal postural balance measures showed significant improvements (eyes open, = 0.02; eyes closed, < 0.01) in the CSTG in posttest compared with pretest session. However, no significant differences ( > 0.05) were observed between CSTG and CG after the training period. CONCLUSION: A 12-week CST improved static (foam surface) and dynamic postural balance, core endurance measures, and HAGOS scores. CLINICAL RELEVANCE: The beneficial effect of CST on improving postural balance, core endurance, and self-reported outcomes in soccer players with GP suggests that this training would be an important feature of rehabilitation programs for these players. Coaches and clinicians should prioritize CST training when designing rehabilitation programs.