AimTo evaluate the effectiveness and safety of nutritional interventions (i.e. nutritional support, dietary patterns and dietary supplements) on cognitive function in cancer survivors.DesignSystematic review.MethodsA systematic and comprehensive search of PubMed, Web of Science, the Cochrane Library, Embase, and CINAHL was conducted from the inception until March 10, 2023. The last search was conducted on December 10, 2023.Reporting MethodPRISMA.ResultsA total of 59 randomized controlled trials were included for analysis. Nutritional support, dietary patterns and dietary supplements improved cognitive function in cancer survivors with no apparent safety concerns. The anti‐inflammatory diet, the fasting‐mimicking diet and the web‐based diet significantly improved cognitive function. Whereas the ketogenic diet or dietary advice to consume more soluble dietary fibres and less insoluble dietary fibres and lactose could not. There was evidence from dietary supplements to support the beneficial effects of polyunsaturated fatty acid supplements, traditional herbal medicines and other supplements.ConclusionsNutritional interventions have great promise for improving cognitive function in adult cancer survivors. Further validation of the nutritional interventions supported in this study in other survivors and exploration of more effective nutritional interventions are needed.Implications for the Profession and/or Patient CareThis work can support the construction of nutritional support interventions and dietary guidance programs to prevent cancer‐related cognitive decline.ImpactThis work filled a gap in preventive strategies for cancer‐related cognitive decline from a nutritional perspective. Nutritional support, dietary patterns, and dietary supplements can prevent cancer‐related cognitive decline without serious safety concerns. This work highlighted nutritional interventions that have the potential to improve cognitive function in cancer survivors, benefiting the further construction of evidence‐based nutritional intervention programs.Protocol RegistrationPROSPERO.Patient or Public ContributionNo patient or public contribution.