Purpose <p>Dry mouth is one of the most common complaints of obstructive sleep apnea (OSA) patients. The extent of the relationship between OSA severity and subjective xerostomia is not yet fully understood.</p> Methods <p>The Multidisciplinary Salivary Gland Society Questionnaire (MSGS) was administered to 120 patients with OSA. All patients underwent polysomnography and a comprehensive physical exam. The association of MSGS scores with objective and subjective OSA measures was evaluated.</p> Results <p>A significant correlation was observed between the xerostomia subscale of MSGS and the percent of sleep time spent with oxygen saturation below 90% (Spearman’s ρ: 0.211, <i>p</i> = 0.028), oxygen saturation nadir (Spearman’s ρ: -0.265, <i>p</i> = 0.005) and Friedman tonsil grade (Spearman’s ρ: 0.333, <i>p</i> = 0.001). A significant association between xerostomia and Modified Cormack-Lehane endoscopic score of larynx (Spearman’s ρ: -0.201, <i>p</i> = 0.042) and a near significant association between xerostomia and endoscopic vertical phenotype of the palate (Spearman’s ρ: -0.194, <i>p</i> = 0.050) were observed. Tonsil grade was also a significant predictor of xerostomia and the total MSGS in multivariate regression analysis (correlation coefficient = 3.3, <i>p</i> = 0.001, and correlation coefficient = 2.6, <i>p</i> = 0.011; respectively). Age was inversely associated with the sialadenitis score, in both univariate and multivariate analyses (correlation coefficient = -3.2, <i>p</i> = 0.002).</p> Conclusion <p>OSA patients with tonsillar hypertrophy and severe sleep hypoxia have higher rates of subjective xerostomia. Further studies are needed to investigate the bidirectional relationship between sleep apnea and xerostomia.</p>