Objective To investigate the association between obstructive sleep apnea (OSA) and laryngopharyngeal reflux (LPR) through oropharyngeal pH-monitoring and pepsin saliva measurements. Design Prospective uncontrolled study. Methods Patients with sleep disturbances and reflux symptoms underwent polysomnography, 24-h oropharyngeal pH-monitoring and saliva pepsin collections. The prevalence of LPR was investigated in OSA patients according to oropharyngeal pH-monitoring and pepsin measurements. A correlation analysis was performed between pH-monitoring findings, pepsin saliva levels, reflux symptom score-12 (RSS-12), reflux sign assessment (RSA), Apnea–Hypopnea Index (AHI), Epworth Sleepiness Scale, Pichot and arousal findings. Results Thirty-seven patients completed the evaluations. LPR was detected in 34/37 (92%) and 29/34 (85%) patients at the oropharyngeal-pH monitoring and pepsin test, respectively. OSA was detected in 30 patients (81%). Among them, LPR was detected in 28/30 (93%) cases. Pharyngeal reflux events mainly occurred nighttime/supine in OSA patients. Both Ryan score and supine reflux time at pH < 6.5 were significantly associated with BMI and the RSA sub- and total scores ( p < 0.02). Tongue-base hypertrophy score was positively associated with the number of micro-arousals ( p = 0.027); the supine percent of pH < 6.5 ( p = 0.030); morning ( p = 0.030) and bedtime pepsin saliva measurements ( p = 0.037). The bedtime pepsin saliva level was significantly associated with Ryan Score ( p = 0.047); AHI ( p = 0.017) and the sleep saturation < 90% time ( p = 0.040). The saliva level of the morning pepsin was associated with a shortest paradoxical sleep phase ( p = 0.013). Conclusion OSA patients may have high prevalence of pharyngeal reflux events at the oropharyngeal pH-monitoring and high pepsin saliva measurements. Oropharyngeal pH-monitoring should be useful for the correlation between reflux and sleep findings in OSA patients. Future large cohort controlled studies are needed to determine the prevalence of LPR in OSA and healthy individuals.