IntroductionThe impact of the COVID-19 pandemic (caused by the SARS-CoV-2 virus) on individuals with cancer has been profound. It has led to increased anxiety, distress and deconditioning due to reduced physical activity. We aim to investigate whether SafeFit, a multimodal intervention of physical activity, nutrition and psychological support delivered virtually by cancer exercise specialists (CES), can improve physical and emotional functionings during the COVID-19 pandemic.Methods and analysisA phase III non-randomised intervention trial, target recruitment of 1050 adults with suspected or confirmed diagnosis of cancer. All recruited participants will receive the multimodal intervention delivered by CES for 6 months. Sessions will be delivered 1-to-1 using telephone/video conferencing consultations. CES will work with each participant to devise a personalised programme of (1) physical activity, (2) basic dietary advice and (3) psychological support, all underpinned by behaviour change support.Primary outcomePhysical and emotional functioning as measured by the European Organisation for Research and Treatment of Cancer-Quality of Life Questionnaire (EORTC-QLQ-C30). Secondary outcomes: overall quality of life measured by EORTC-QLQ-C30 and EQ-5D-5L, health economics, patient activation, self-efficacy to self-manage chronic disease, distress, impact of COVID-19 on emotional functioning, self-reported physical activity, functional capacity and nutrition. Adherence to the intervention will also be measured and a process evaluation conducted.Ethics and disseminationEthical approval was obtained from the Health Research Authority (reference number 20/NW/0254). Results of this trial will be disseminated through publication of peer-reviewed articles, presentations at scientific conferences, and to the public and people with cancer in collaboration with our patient and public involvement representatives and partners.Trial registration numberNCT04425616.