IntroductionSuicidal behaviour remains a major public health challenge worldwide. Several countries have developed national suicide guidelines aimed at raising awareness of and preventing deaths by suicide. One of the interventions often mentioned in these national guidelines is the involvement of family members as a protective factor in suicide prevention. However, the level or type of family involvement required to reduce suicidal behaviour is not well understood. Thus, in this systematic review, we seek to determine the effectiveness of family-based interventions as a suicide prevention tool, by comparing suicide mortality rates between countries whose national suicide prevention guidelines include family-based interventions and those whose do not.Methods and analysisMEDLINE, EMBASE, PsycINFO, Web of Science and WHO MiNDbank databases as well as grey literature such as National Guideline Clearinghouse will be searched. National guidelines for suicide prevention published within the last 20 years (between 1999 and 2019) will be included. Results will be analysed using thematic and qualitative analyses.Ethics and disseminationThe findings of the study will help improve the efficacy of national suicide prevention strategies. Findings will be disseminated using easily accessible summary reports and resources to primary end users.PROSPERO registration numberThis protocol has been registered on PROSPERO (CRD42019130195).