Altered sleep-wake behaviours including reduced physical activity and poor sleep, contributes to cancer incidence. Yet, how a cancer diagnosis contributes to altered sleep-wake behaviours remains less understood. Understanding these changes is crucial given the significant risk of comorbidities, poor psychological wellbeing, and cancer-related mortality. This study compared the sleep-wake behaviour profiles among adults with cancer to healthy adults using data from 32,989 participants in the UK Biobank. The potential influence of time since cancer diagnosis (<1 year, 1-5 years, and >5 years) and cancer type on sleep-wake behaviours was also investigated. Sleep-wake behaviours were measured using accelerometers and cancer diagnosis was identified through a cancer registry linked to UK Biobank participants. Compositional data analysis was employed to estimate the minutes spent in each sleep-wake behaviour, including moderate-to-vigorous physical activity (MVPA), light physical activity (LPA), sedentary behaviour, and sleep period. It was found adults with cancer spent significantly less time in physical activity, 7.62 and 13.93 minutes shorter in MVPA and LPA, respectively, compared to healthy adults. However, they spent more time in inactive behaviours, 12.78 and 8.77 minutes longer in sedentary behaviour and sleep period, respectively. Adults diagnosed with cancer <1 year prior and adults with Blood, Gastrointestinal, or Lung cancers experienced the greatest disruptions in their sleep-wake behaviours compared to healthy adults. Conversely, adults diagnosed with Colorectal, Other Skin and Prostate cancers showed the least differences from healthy adults. Results highlighted adults with cancer engaged in less physical activity and more time in inactive behaviours compared to healthy adults. Interventions may prioritise increasing physical activity while simultaneously reducing sedentary behaviour. Furthermore, a cancer diagnosis, time since diagnosis, and cancer type, are important contributing factors to altered sleep-wake behaviours. Health practitioners may consider these factors to optimise behavioural interventions for adults with cancer.