Purpose This review and meta-analysis aimed to evaluate the effects of high-intensity interval training (HIIT) compared to usual care (UC) or moderate-intensity training (MIE) on physical fitness and health-related outcomes in cancer patients across all stages of therapy and aftercare. Methods Databases were systematically searched in accordance with the PRISMA guidelines until October 4th, 2018. Eligibility criteria included adult patients of various cancer types, performing HIIT vs. UC or MIE. Outcomes of interest included physical fitness (cardiorespiratory fitness [VO2peak] and functional capacity) and health-related outcomes (body composition, quality of life, cancerrelated fatigue, and blood-borne biomarkers). Mean differences (MD) were calculated and pooled to generate effect sizes for VO2peak. Results The search identified 1453 studies, out of which 12 articles were included. The average duration of interventions was 6.7 ± 3.0 weeks, with 2.8 ± 0.5 sessions per week. The meta-analysis for VO2peak showed superiority of HIIT compared to UC (MD 3.73; 95% CI 2.07, 5.39; p < 0.001) but not MIE (MD 1.36; 95% CI − 1.62, 4.35; p = 0.370). Similarly, no superior effects of HIIT compared to MIE were found for quality of life or changes in lean mass, while evidence was provided for a larger reduction in fat mass. Conclusion This systematic review showed that short-term HIIT induces similar positive effects on physical fitness and healthrelated outcomes as MIE but seems to be superior compared to UC. Thus, HIIT might be a time-efficient intervention for cancer patients across all stages of therapy and aftercare. Implications for Cancer Survivors High-intensity interval training (HIIT) is superior compared to usucal care in improving physical fitness and health-related outcomes in cancer patients across all stages of therapy and aftercare. Currently, there is no evidence for the benefits of HIITcompared to aerobic training of moderate intensity (MIE) for changes in cardiorespiratory fitness, lean mass and patientreported outcomes. Reductions in fat mass may be more pronounced in HIIT compared to MIE when training is performed in aftercare