BACKGROUND: Trauma is a major cause of mortality in the elderly population. Hyponatremia is the most common electrolyte imbalance in geriatric patients and has been demonstrated to be a risk factor for altered cognition, low bone density, falls, and death. We systematically and critically reviewed the literature to ascertain the association between hyponatremia and geriatric trauma outcomes. METHODS: We searched seven databases for articles published from inception to October 2023. Studies included reported on geriatric trauma, hyponatremia, and clinical outcomes. Two investigators independently reviewed 6535 abstracts, 235 full-text articles, and critically appraised each study. Study details, patient characteristics, and outcomes were independently extracted by two reviewers. Data quality assessment was performed using the Grading of Recommendations Assessment, Development, and Evaluation approach. Publication bias was assessed using funnel plot-based methods. A meta-analysis of risk ratios (RR) was performed using the random effects method. RESULTS: Four retrospective cohort studies involving 11 894 geriatric patients were included. Among these, 492 (21.4%) were classified as trauma patients due to a fall and 1806 (78.6%) were classified as a trauma patient due to the presence of a fracture. In total, 2298 (19.3%) patients were classified as hyponatremic (125-135 mmol/L) while 9596 (80.7%) were classified as normonatremic. The pooled RR for in-hospital mortality for hyponatremic patients was 2.23 (95% CI 1.51 to 3.74) with high heterogeneity across the studies (I CONCLUSIONS: Geriatric trauma patients presenting with hyponatremia appear to have an increased risk of in-hospital mortality. Given this association, national trauma registries should consider collecting serum sodium values for geriatric patients and providers should work to address hyponatremia as a possible contribution to falls. Given the paucity of published literature on this topic, there is a need for prospective studies evaluating the association between hyponatremia and geriatric trauma outcomes. LEVEL OF EVIDENCE: Level III, systematic review with meta-analysis.