Abstract Background Hypernatremia is a common electrolyte disturbance in hospitalised patients associated with adverse outcomes. The aetiology is diverse but often related to fluid therapy and sodium‐containing medicaments. We aim to outline the evidence base on hypernatremia in adult hospitalised patients. Methods We will conduct a scoping review and adhere to the preferred reporting items for systematic and meta‐analysis extension for scoping reviews (PRISMA‐ScR). We will systematically search the Cochrane Library, Medline, Pubmed, and Embase from inception with no limitations to language, and include all study designs. We will use the population, exposure, comparator, and outcome‐based approach to define eligibility criteria. The population: adult hospitalised patients; exposure: hypernatremia; comparator: no hypernatremia or all types of treatments of hypernatremia; and outcomes: all reported outcomes. Two authors will independently screen and select studies followed by full‐text assessment and data extraction in duplicate. All outcome measures will be reported, and descriptive analyses will be performed. The certainty of evidence will be assessed according to an adapted grading of recommendations assessment, development, and evaluation (GRADE) approach. Discussion This scoping review will provide an overview of the current evidence regarding the incidence of hypernatremia, treatment modalities, and outcomes reported for hospitalised adult patients with hypernatremia.