Obstructive sleep apnea syndrome (OSAS) is a common health problem, and associated with obesity, metabolic syndrome (MetS), and diabetes. Growing evidence shows that 25-hydroxyvitamin-D-3 (25-OH-D) insufficiency and high parathyroid hormone (PTH) levels may be correlated to glucose intolerance, MetS, obesity, and cardiovascular abnormalities similar to OSAS. Bisphenol A (BPA) is an endocrine disruptor agent which exerts a wide variety of metabolic effects. It has estrogenic activity and its exposure may contribute to weight gain, obesity, impaired glucose metabolism, and the development of diabetes, also similar to OSAS. The aim of this study is to investigate the relationships between OSAS and serum BPA, 25-OH-D, and PTH levels. This study enrolled 128 subjects, with all of the OSAS patients having been diagnosed by polysomnography. The 128 subjects were divided into three groups: a control (n = 43), a moderate OSAS (n = 23) (AHI = 15-30), and a severe OSAS groups (n = 62) (AHI > 30). The serum BPA, 25-OH-D, and PTH levels for each subject were analyzed. 25-OH-D was lower in both OSAS groups, and PTH was higher in the OSAS groups than in the control subjects. The BPA levels were higher in the severe OSAS group than the moderate OSAS and control. There was a positive correlation between the BPA and body mass index, and a negative correlation between the 25-OH-D and BPA levels in all of the individuals. OSAS is related to high BPA and PTH levels, and low vitamin D levels. There is a positive association between BPA levels and OSAS, and the severity of OSAS. These results suggest that the BPA levels may have a role in the pathogenesis of OSAS.