Research recognizes the extent of harm experienced by concerned significant others (CSOs) of gamblers. This systematic review’s aims are to examine the interventions for CSOs, evaluate potential benefits, and thematically describe treatment processes. The Stress-Strain-Coping-Support model (SSCS) served as the theoretical framework.

Database searches were conducted in: MEDLINE, CINAHL Complete, Web of Science Core Collection, Social Services Abstracts, Applied Social Science Index and Abstracts, Cochrane Central Register of Controlled Trials, and APA PsycInfo (between 01/Jan 2011–10/Jun 2021). Other search methods were also utilized. Inclusion criteria: interventions for CSOs with CSO specific outcomes. The Evidence Project Risk of Bias Tool was used for assessment.

19/768 records were included. Nine interventions were utilized: 3 CSO directed, 4 for couples, and 2 low threshold online interventions. A quantitative synthesis (N = 7 studies) of effect size estimates for depression and anxiety measures didn’t indicate any intervention to have better outcomes than others. Core themes in the treatment process identified in the qualitative synthesis (N = 7) included: information and understanding, social support, coping skills, communication, and strain. Limitations in the evidence related to sampling, control-conditions and outcome measurements.

Several interventions were identified, yet no specific interventions appeared more beneficial than others. Using the SSCS model, commonalities and differences in intervention content were identified, along with themes that influence treatment processes. The need for tailored interventions is discussed. Future treatment efficacy research should carefully select study designs and outcome measurements. PROSPERO (CRD42021229408).