The role of probiotics in trauma patients remains unclear. We undertook a meta-analysis of published randomized controlled trials (RCTs) to assess the effects of probiotics on the clinical outcomes of trauma patients. A systematic electronic literature search was conducted to identify RCTs comparing the use of probiotics with a control in trauma patients. Results were expressed as risk ratios (RRs) or standardized mean differences (SMDs) with accompanying 95% confidence intervals (CIs). The primary outcome measurement was the incidence of nosocomial infections. Secondary outcome measurements included the incidence of ventilator-associated pneumonia (VAP), length of intensive care unit (ICU) stay, and mortality. The meta-analysis was performed with the fixed-effect or random-effect model according to the heterogeneity. Five studies involving 281 patients met our inclusion criteria. The use of probiotics was associated with a reduction in the incidence of nosocomial infections (5 trials; RR, 0.65; 95% CI, 0.45-0.94, P = .02), VAP (3 trials; RR, 0.59; 95% CI, 0.42-0.81, P = .001), and length of ICU stay (2 trials; SMD, -0.71; 95% CI, -1.09 to -0.34, P < .001) but no reduction in mortality (4 trials; RR, 0.63; 95% CI, 0.32-1.26, P = .19). The use of probiotics is associated with a reduction in the incidence of nosocomial infections, VAP, and length of ICU stay but is not associated with an overall mortality advantage. However, the results should be interpreted cautiously due to the heterogeneity among study designs. Further large-scale, well-designed RCTs are needed.