Sleep bruxism (SB) is a common disorder that presents as repetitive jaw muscle activity with clenching or grinding of teeth and/or bracing or thrusting of the mandible. Several studies have suggested that SB is associated with obstructive sleep apnea (OSA). However, the effect of treatment with continuous positive airway pressure (CPAP) on SB concomitant with OSA has not been well recognized, except in a few reported cases. Herein, we present three cases of SB with various OSA severities that were successfully treated with CPAP, as indicated by the improvement in their clinical symptoms and bruxism index on polysomnography. Our results suggest that clinicians should raise suspicion of OSA in patients with SB and be aware that patients with SB and concomitant moderate-to-severe OSA can be successfully treated with CPAP.