Background Cancer-related fatigue can continue long after curative cancer treatment. The aim of this study was to investigate sleep and rest-activity cycles in fatigued and non-fatigued cancer survivors. We hypothesized that sleep and rest-activity cycles would be more disturbed in people experiencing clinically-relevant fatigue, and that objective measures of sleep would be associated with the severity of fatigue in cancer survivors. Methods: Cancer survivors (n=87) completed a 14-day wrist actigraphy measurement for the estimation of sleep and rest-activity cycles. Fatigue was measured using the Functional Assessment of Chronic Illness Therapy-Fatigue Scale (FACIT-F). Participants were dichotomised into two groups using a previously validated score (fatigued n=51 and non-fatigued n=36). Perception of sleep was measured using the Insomnia Severity Index (ISI). Results: FACIT-F score was correlated with wake after sleep onset (r =-0.28; p = 0.010), sleep efficiency (r=0.26; p=0.016), sleep onset latency (r=-0.31; p=0.044) and ISI score (r=-0.56; p <0.001). The relative amplitude of the rest-activity cycles was lower in the fatigued vs. non-fatigued group (p=0.017; d=0.58). Conclusions: After treatment for cancer, the severity of cancer-related fatigue is correlated with specific objective measures of sleep, and there is evidence of rest-activity cycle disruption in people experiencing clinically-relevant fatigue.