Abstract Context Polycystic ovary syndrome (PCOS) is a common endocrine disorder and is associated with metabolic syndrome (MS). Development of MS in PCOS is likely multifactorial and may relate to poor sleep. Objective The objective of this research is to investigate differences in objective markers of sleep in adolescents with obesity and PCOS with and without MS. We also aimed to examine the relationships between markers of sleep with MS markers. Design A cross-sectional study was conducted. Participants Participants included adolescents with PCOS and obesity with MS (N = 30) or without MS (N = 36). Outcome Measures Hormone and metabolic measurements, abdominal magnetic resonance imaging for hepatic fat fraction, actigraphy to estimate sleep, and overnight polysomnography (PSG). Results Adolescents with obesity and PCOS who also had MS had significantly worse sleep-disordered breathing including higher apnea-hypopnea index (AHI, P = .02) and arousal index (P = .01) compared to those without MS. Actigraphy showed no differences in habitual patterns of sleep behaviors including duration, timing, or efficiency between groups. However, a greater number of poor sleep health behaviors was associated with greater number of MS components (P = .04). Higher AHI correlated with higher triglycerides (TG) (r = 0.49, P = .02), and poorer sleep efficiency correlated with higher percentage of liver fat (r = –0.40, P = .01), waist circumference (r = –0.46, P < .01) and higher TG (r = –0.34, P = .04). Conclusions Among girls with PCOS and obesity, sleep-disordered breathing was more prevalent in those with MS, and poor sleep behaviors were associated with metabolic dysfunction and more MS symptoms. Sleep health should be included in the assessment of adolescents with PCOS and obesity.