BackgroundStudies assessing the nutritional quality of food provided to the homeless population show deficiencies in micronutrients and excess fat, sugar, and salt. The availability of cheap, energy-dense and nutrient-poor food has changed the profile of people living with homelessness from primarily underweight to obese in western countries. Many factors influence the nutritional quality of food provided to the homeless population such as budget and time constraints, food donations and limited equipment. Nutrient intakes in this population are unlikely to be met outside of charitable meal programmes, making the nutritional quality of these meals crucial. This review will synthesise mixed methods literature with the overarching aim of understanding the determinants of the nutritional quality of food provided to the homeless population.MethodsThis mixed methods systematic review will include English language empirical research studies from Europe, North America and Oceania. The following electronic databases have been chosen for this review: SCOPUS, EMBASE, PsycINFO, EBSCOHost SocIndex and CINAHL. The grey literature databases OpenGrey and ProQuest will also be searched. Quality appraisal will be conducted using the Mixed-Methods Appraisal Tool. Two independent reviewers will be included in study selection, data extraction and quality appraisal. A third reviewer will resolve conflicts. Thematic synthesis will be employed.DiscussionResults will be organised based on a determinants of health model, to highlight areas where change may be effective, thereby making it more likely to be useful to practitioners and researchers. The iterative steps in the systematic review process will be the focus of this article. Findings from this review will be used to develop best-practice guidelines for stakeholders such as policy makers and service providers to improve the nutritional quality of food provided in the homeless sector.Systematic review registrationThis mixed methods systematic review protocol has been registered with the International Prospective Register of Systematic Reviews (PROSPERO): CRD42021289063.