BACKGROUND: Cancer-related fatigue (CRF) is one of the most prevalent symptoms in individuals with cancer. Various types of exercise have shown beneficial effects. While previous systematic reviews suggest exercise may improve CRF and quality of life, evidence specifically about yoga's impact, as well as evidence on long-term effects, is limited. Previous syntheses offer promising but inconclusive findings on yoga's effectiveness. This review is one of a suite of five reviews exploring exercise for cancer-related fatigue. OBJECTIVES: To assess the effects of yoga versus no yoga on cancer-related fatigue in people with cancer: • before, during, and after anticancer treatment; • in the short, medium, and long term; • and effects on quality of life (QoL), adverse events, depression, and anxiety. SEARCH METHODS: We used CENTRAL, MEDLINE, Embase, five other databases and two trials registers, together with reference checking, citation searching and contact with study authors to identify studies that are included in the review. The latest search date was October 2023. SELECTION CRITERIA: We included randomised controlled trials (RCTs) comparing yoga to no yoga. We included studies in adults (aged 18 and older) with any type of cancer and anticancer therapy who received yoga before, during, or after anticancer therapy. We included trials evaluating at least one of the main outcomes (CRF or QoL). Yoga had to last for at least five sessions, and involve face-to-face instruction. We excluded trials with fewer than 20 participants randomised per group. DATA COLLECTION AND ANALYSIS: The outcomes of interest in this review are cancer-related fatigue (CRF), quality of life (QoL), adverse events, depression, and anxiety. We used standard methods expected by Cochrane. For analyses, we pooled results within the same period of outcome assessment (i.e. short, medium, and long term), and employed a random-effects model. We assessed risk of bias with the Cochrane risk of bias (RoB) 1 tool, and used GRADE to assess the certainty of the evidence. MAIN RESULTS: We included 21 RCTs with 2041 people with cancer who received yoga during (13 studies) or after (eight studies) anticancer therapy; none examined yoga initiated before therapy. Here we present results on CRF and QoL; findings on adverse events, depression, and anxiety are in the full review. Yoga during anticancer therapy The evidence is very uncertain about the effect of yoga compared to no yoga on: short-term CRF (standardised mean difference (SMD) 0.07, 95% confidence interval (CI) -0.18 to 0.32; mean difference (MD) on Brief Fatigue Inventory (BFI; lower values mean better outcome) of 0.16, 95% CI -0.41 to 0.71; 3 studies, 253 participants); medium-term CRF (MD on Multidimensional Fatigue Inventory (MFI; lower values mean better outcome) of -1.30, 95% CI -3.50 to 0.90; 1 study, 67 participants); and long-term CRF (MD 0.09 on BFI, 95% CI 1.16 to 0.98; 2 studies, 155 participants) (all very low-certainty evidence). Yoga may have a small beneficial effect or no effect compared to no yoga on short-term QoL (SMD 0.25, 95% CI 0.04 to 0.45; MD on Quality of Life Questionnaire-C30 (QLQ-C30; higher values mean better outcome) of 5.28, 95% CI 0.84 to 9.56; 4 studies, 374 participants) and medium-term QoL (MD on QLQ-C30 of 7.63, 95% CI 6.71 to 21.97; 2 studies, 151 participants), but the evidence is very uncertain (all very low-certainty evidence). None of the included studies reported long-term QoL. Yoga after anticancer therapy Yoga probably has a beneficial effect compared to no yoga on short-term CRF (SMD -0.26, 95% CI -0.42 to -0.09; MD 2.55, 95% CI 0.88 to 4.12; higher values mean better outcome; 5 studies, 602 participants; moderate-certainty evidence). Yoga might have a beneficial effect or no effect compared to no yoga on medium-term CRF, but the evidence is very uncertain (MD 3.02, 95% CI -1.48 to 7.52; 1 study, 54 participants (higher values mean better outcome; very low-certainty evidence). None of the included studies reported long-term CRF. Yoga may have a small beneficial effect or no effect compared to no yoga on short-term QoL (SMD 0.19, 95% CI -0.09 to 0.47; MD -3.27, 95% CI -8.08 to 1.55; higher values mean better outcome; 4 studies, 275 participants) and medium term QoL (MD 7.06, 95% CI -1.38 to 15.50; 1 study, 54 participants; higher values mean better outcome), but the evidence is very uncertain (all very low-certainty evidence). None of the included studies reported long-term QoL. A key limitation of the review was the included studies' methodological constraints: participants' awareness of treatment assignments (yoga or control) potentially introduced bias. Additionally, sample sizes were too small to determine medium- and long-term effects conclusively. Further research is needed to evaluate the sustainability of yoga's impact on cancer-related fatigue, quality of life, and adverse events. AUTHORS' CONCLUSIONS: Our review provides uncertain evidence of the beneficial effects of yoga initiated during or after anticancer therapy compared to no yoga for people with cancer. Although there are indications supporting the use of yoga to address CRF, the uncertainty of the evidence underscores the need for caution in its implementation. Future RCTs should employ rigorous methodologies, enrol sufficient participants, and use appropriate controls.