Purpose: To identify the association between nocturia and obstructive sleep apnea (OSA), we compared results of polysomnography (PSG) with the presence or absence of nocturia in patients with suspected OSA. Methods: Patients underwent PSG for suspected OSA. The International Prostate Symptom Score and quality of life (IPSS/ QoL) questionnaire was evaluated to assess voiding symptoms that may affect sleep quality. The results of PSG were compared between patient groups with or without nocturia. Results: In logistic regression analysis, age (odds ratio [OR], 1.052; P = 0.004), diabetes mellitus (OR, 6.675; P < 0.001), mean O2 saturation (OR, 0.650; P = 0.017), oxygen desaturation index (ODI) 3 (OR, 1.193; P = 0.010), and ODI4 (OR, 1.136; P = 0.014) affected nocturia independently among the OSA-suspected patients. Conclusions: Hypoxia caused by OSA affects the incidence of nocturia. Less desaturated OSA patients with nocturia may require more urological evaluation and treatment for nocturia even after the correction of OSA.