IntroductionSocial isolation and loneliness affect approximately one-third to one-half of the elderly population and have a negative impact on their physical and mental health. Group-based interventions where facilitators are well trained and where the elderly are actively engaged in their development seem to be more effective, but conclusions have been limited by weak study designs. We aim to conduct a systematic review to assess the effectiveness of health promotion interventions on social isolation or loneliness in older people.Methods and analysisA systematic review was conducted in Medline, Embase, PsycINFO, Cumulative Index to Nursing and Allied Health Literature, Applied Social Sciences Index and Abstracts, LILACS, OpenGrey and the Cochrane Library on peer-reviewed studies and doctoral theses published between 1995 and 2016 evaluating the impact of health promotion interventions on social isolation and/or loneliness for individuals aged 60 and over. Two reviewers will independently assess each study for inclusion and disagreements will be resolved by a third reviewer. Data will be extracted using a predefined pro forma following best practice. Study quality will be assessed with the Effective Public Health Practice Project quality assessment tool. A narrative synthesis of all studies will be presented by type of outcome (social isolation or loneliness) and type of intervention. If feasible, the effectiveness data will be synthesised using appropriate statistical techniques.Ethics and disseminationThis systematic review is exempt from ethics approval because the work is carried out on published documents. The findings of the review will be disseminated in a related peer-reviewed journal and presented at conferences. They will also contribute to a DPhil thesis.Trial registration numberCRD42016039650