PurposeCancer and its therapy causes severe symptoms, most of which are amendable to nutrition and physical activity (PA). Counselling on nutrition and PA empowers patients to take part more actively in their treatment. Many cancer patients are yet in need of information on these topics. In this study, we investigate the perception of family physicians (FP) on nutrition and PA in cancer patient care and assess barriers and steps to improve their involvement in counselling on these topics.MethodsBased on qualitative content analysis of 5 semi-structured interviews with FP, a questionnaire was developed and completed by 61 German FP.ResultsMost of the FP acknowledged the importance of nutrition and PA during (91.4%) and after (100%) cancer therapy. While many participants were involved in cancer patient care, 65.6% of FP viewed themselves as primary reference person to address these topics. However, a third (32.8%) of FP were unfamiliar with information thereof. Some were unsatisfied regarding timely updates on their patient’s treatment course via discharge letters (25.0%) or phone calls (36.2%). FP would like to dedicate more consultation time addressing nutrition and PA than they currently do (p< 0.001).ConclusionCommunication btween healthcare practitioners about mutual cancer patient’s treatment must be improved, e.g. utilising electronic communication to quicken correspondence. Acquisition of information on nutrition and PA in cancer patient care needs to be facilitated for FP, approachable by compiling reliable information and their sources. Involvement of FP in structured treatment programs could benefit cancer patient care.Trial registration number(May 7, 2021): 2021–2149-Bef.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00432-022-04233-5.