Background: Excess body weight and heavy alcohol consumption are two of the greatest contributors to global disease. Alcohol use peaks in early adulthood. Alcohol consumption can also exacerbate weight gain. A high body mass index and heavy drinking are independently associated with liver disease but, in combination, they produce an intensified risk of damage, with individuals from lower socio-economic status groups disproportionately affected. Methods: We will conduct searches in MEDLINE, Embase, PubMed, PsycINFO, ERIC, ASSIA, Web of Knowledge (WoK), Scopus, CINAHL via EBSCO, LILACS, CENTRAL and ProQuest Dissertations and Theses for studies that assess targeted preventative interventions of any length of time or duration of follow-up that are focused on reducing unhealthy eating behaviour and linked risky alcohol use in 18-25-year-olds. Primary outcomes will be reported changes in: (1) dietary, nutritional or energy intake and (2) alcohol consumption. We will include all randomised controlled trials (RCTs) including cluster RCTs; randomised trials; non-randomised controlled trials; interrupted time series; quasi-experimental; cohort involving concurrent or historical controls and controlled before and after studies. Database searches will be supplemented with searches of Google Scholar, hand searches of key journals and backward and forward citation searches of reference lists of identified papers. Search records will be independently screened by two researchers, with full-text copies of potentially relevant papers retrieved for in-depth review against the inclusion criteria. Methodological quality of RCTs will be evaluated using the Cochrane risk of bias tool. Other study designs will be evaluated using the Cochrane Public Health Review Group's recommended Effective Public Health Practice Project Quality Assessment Tool for Quantitative Studies. Studies will be pooled by meta-analysis and/or narrative synthesis as appropriate for the nature of the data retrieved. Discussion: It is anticipated that exploration of intervention effectiveness and characteristics (including theory base, behaviour change technique; modality, delivery agent(s) and training of intervention deliverers, including their professional status; and frequency/duration of exposure) will aid subsequent co-design and piloting of a future intervention to help reduce health risk and social inequalities due to excess weight gain and alcohol consumption. Systematic review registration: PROSPERO CRD42016040128.