Various research studies demonstrate the positive effects of physical activity (PA) on sleep quality in healthy and patient populations, but limited work has analyzed this relationship in pediatric oncology samples. Our research aimed to fill this gap by examining the relationships between PA and sleep in adolescent and young adult (AYA) cancer patients, assessing levels of both with an accelerometer (ActiGraph G9TX). Participants completed a baseline questionnaire on sleep disturbances, sleep-related impairment, and fatigue and wore the accelerometer on their non-dominant wrist for two weeks. Moderate-to-vigorous PA (MVPA) levels were determined using the Lee cutpoint for young adults, and sleep periods were identified by the ActiLife program and manually verified with patient-reported sleep logs. Sleep was scored using the Sadeh algorithm and Pearson's correlation tests were used to determine relationships between MVPA and sleep outcomes. Overall, there was a nonsignificant correlation between MVPA and Total Sleep Time (TST) (r= -.23, p= .39), but it became significant when controlling for sex (r= -.55, p = .029). MVPA was also not significantly correlated with Wake After Sleep Onset (WASO) (r= .24, p= .35) or any of the self-reported sleep outcomes. Contrary to our hypothesis, patients who were more active spent less time asleep. This may be due to varying intensity or types of cancer treatments, as patients experiencing more intense symptoms may have more barriers to engaging in MVPA and require more sleep. Future work in a larger sample of AYA, controlling for potential confounders including types and intensity of treatment, is necessary to further understand these relationships.