Obstructive sleep apnea (OSA) has been reported to be a cause of hypertension in 40-80% of hypertensive patients. However, there are limited data available on the prevalence and predictors of OSA in young hypertensive patients. This study was conducted between October 2017 and October 2018. The inclusion criteria were (1) age over 18 and under 35 years (2) diagnosis with hypertension and (3) available respiratory polysomnography results. Patients with other causes of secondary hypertension were excluded. Predictors for OSA were analyzed using multivariate logistic regression analysis. There were 593 consecutive young patients who were diagnosed with hypertension during the study period. Of those, 475 (80.10%) were excluded due to their hypertension having renal causes (429; 90.32%), endocrine-related causes (40; 8.42%), or cardiovascular causes (6; 1.26%). Of the remaining patients (118 patients) who were eligible for the study, 105 (88.98%) of whom were diagnosed with OSA. The median age of the patients with OSA did not differ from those without OSA (29 vs 23 years; p value 0.065). There were two independent predictors for OSA: age and body mass index with adjusted odds ratios (95% confidence interval) of 1.280 (1.049, 1.562) and 1.258 (1.083, 1.462), respectively. In conclusion, after excluding other possible causes of hypertension, we found OSA to be highly prevalent in hypertensive patients younger than 35 years old. Increasing age and high body mass index were predictors for OSA in young hypertensive patients.