Early recovery from muscular injury is crucial for elite athletes. Hyperbaric oxygen therapy (HBOT) has been reported to be beneficial in terms of accelerating cell recovery and tissue repair, which are considered to be helpful for eliminating fatigue and recovering stamina. This study was performed to evaluate the efficacy of HBOT for exercise-related muscular injury. Forty-one athletes with exercise-related muscular injuries were recruited and randomized into an HBOT group and a control group. All participants received 10 sessions of either HBOT or placebo treatment. The brief pain inventory (BPI) was completed, and serum samples were analyzed. Data were collected before treatment (T1), at the end of the fifth treatment session (T2), at the end of the tenth treatment session (T3), and two weeks after T3 (T4). At T3, the HBOT group showed prominent reductions in the levels of creatine phosphokinase (CK), glutamic oxaloacetate transaminase (GOT), and myoglobin (MB), which lasted until T4. However, the control group did not present any statistical differences in levels from T1 to T4. In terms of pain intensity and interference, the HBOT group showed significant improvements at T3, while no improvements were observed in the control group. In conclusion, HBOT facilitates the early recovery of exercise-related muscular injury. This trial is registered with ISRCTN17817041.