Background: Almost 40 million family caregivers care for a loved one with severe physical or cognitive impairments. The purpose of this review is to summarize evidence about the benefits of interventions to support or involve family members/caregivers of patients with trauma-related injury on caregiver, patient, and household outcomes. Methods: English-language peer-reviewed publications in MEDLINE, CINAHL, and PsycINFO from 1995 through December 2016 were identified. Eligible studies included RCT or quasi-experimental studies evaluating interventions designed to support or involve caregivers or family members of patients with TBI, PTSD, or polytrauma. Abstractions were completed by one reviewer and checked by a second; two reviewers independently assessed risk of bias using the Cochrane Effective Practice and Organization of Care Review Criteria. Results: Thirteen studies (n = 9 TBI; n = 4 PTSD, n = 0 polytrauma) evaluated psychological or rehabilitation interventions involving caregivers. Interventions did not improve TBI patients' functional status (standardized mean difference [SMD], 0.29 [95% confidence interval [CI], - 0.51 to 1.08]) or psychological symptoms (SMD - 0.25, CI - 0.62 to 0.12). Qualitative analysis shows potential intervention benefit for TBI symptoms. Interventions did not improve TBI caregiver psychological symptoms (SMD - 0.26, CI - 0.57 to 0.05); however, qualitative analysis suggests mixed effects for caregiver burden and quality of life. Positive intervention effects on patients' PTSD symptoms, mental health service use, and PTSD caregivers' psychological symptoms were identified with certain interventions. Strength of evidence ranged from moderate to very low. Discussion: Studies showed mixed patterns of intervention effects on caregiver and patient outcomes; evidence about intervention impact is inconclusive. This review is the first to identify caregiving interventions for patients with TBI and polytrauma and extends past reviews about patients with PTSD. Limitations include a small evidence base, low study quality, disparate methods, varied outcome measures, and high heterogeneity. PROSPERO Registration CRD42017053516.