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. Cancer survivors ( = 87) completed a 14-day wrist actigraphy measurement to estimate their 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 = 51 and non-fatigued = 36). The participant's perception of sleep was measured using the Insomnia Severity Index (ISI). FACIT-F score was correlated with wake after sleep onset ( = -0.28; = 0.010), sleep efficiency ( = 0.26; = 0.016), sleep onset latency ( = -0.31; = 0.044) and Insomnia Severity Index (ISI) score ( = -0.56; < 0.001). The relative amplitude of the rest-activity cycles was lower in the fatigued vs. the non-fatigued group ( = 0.017; = 0.58). 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.