AimTo identify and map the evidence on interventions facilitating the involvement of relatives of patients with an acquired brain injury (ABI) or a malignant brain tumour (MBT).BackgroundAn ABI or a MBT are severe diseases that have profound impact on the lives of patients and their relatives. The well‐being of the patient may be deteriorated, and relatives may experience a new role and changing caregiving tasks. Involvement of relatives seems essential, and there is a need for identifying interventions facilitating the involvement.DesignScoping review.MethodsThe Joanna Briggs Institute methodology was used in this review and the review was reported in accordance with the PRISMA extension for scoping reviews.Data SourcesThe literature search was conducted in MEDLINE, Embase, CINAHL and Cochrane Library. Reference lists of included studies, Google Scholar and Web of Science were also searched.ResultsIn total, 46 studies were included of which 36 (78%) involved patients with stroke. Median duration of study interventions were 8 weeks, and nurses were involved as providers of the intervention in 23 (50%) studies. Thirty (65%) studies used a multicomponent intervention. Thirty‐five unique outcomes were identified using 60 unique outcome measurements.ConclusionInterventions facilitating the involvement of relatives differed importantly in key characteristics of study interventions, and in relation to the context in which they were used. There was no consensus regarding choice of outcomes and outcome measurements. Our results highlight the complexity of interventions in this field.Implications for the Profession and/or Patient CareTo our knowledge this is the first scoping review examining interventions facilitating the involvement of relatives of patients with an acquired brain injury or a malignant brain tumour. This review suggests a clear definition of ‘involvement’ in future research and there is a need of development of a core outcome set for use in interventions facilitating the involvement.Reporting MethodThe scoping review was reported in accordance with the PRISMA extension for scoping reviews.No Patient or Public ContributionThe authors decided to undertake this scoping review without patient and public contribution. However, the protocol was published prior to review conduct and available to the public but we did not receive any comments on it.