Obstructive sleep apnea negatively impacts objectively measured physical activity Abstract Purpose Obesity and obstructive sleep apnea (OSA) are frequent comorbid conditions. The impact of OSA on objectively measured physical activity (PA), independent of obesity, is not clear. The purpose of this study is to examine the effect of OSA on PA measured via accelerometer. Methods Overweight-to-obese individuals were recruited and screened for the presence of OSA via portable diagnostic device and divided into an OSA (n = 35) and control group (n = 24). Daytime sleepiness was assessed with the Epworth Sleepiness Scale. Body composition was assessed with dual-energy X-ray absorptiometry. Subjects wore an accelerometer (Actigraph GT3X+, Actigraph Corp., Pensacola, FL) for a minimum of 4 and maximum of 7 days, including at least one weekend day. Results There were no group differences in body mass index (BMI) or daytime sleepiness. Waist and neck circumference were higher in the OSA group. The OSA group was significantly older than the control group. The OSA group had fewer steps, moderate intensity minutes, moderate-to-vigorous minutes, number of PA bouts per day (≥ moderate intensity PA for ≥ 10 consecutive minutes), and total number of PA bouts. When adjusted for age, the PA bout data was no longer significant. Conclusion Individuals screened as likely possessing OSA were less physically active than individuals without OSA when measured through objective means. We found no group differences in daytime sleepiness, BMI, or percent fat, suggesting other mechanisms than obesity and sleepiness for this difference.