OBJECTIVE: This meta-analysis assessed the effectiveness of probiotics and synbiotics for acute diarrhea (AD) in children and investigated probiotic formulations, types of interventions, and country factors. METHODS: Randomized, double-blind, placebo-controlled trials evaluating the effects of probiotics or synbiotics on AD were analyzed. We followed the recommendations of the Cochrane Handbook and the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. The risks of systematic errors (bias) and random errors were assessed, and the overall quality of the evidence was evaluated using the Grades of Recommendations Assessment, Development, and Evaluation (GRADE) approach. RESULTS: The meta-analysis included 34 studies with 4911 patients. Five and 29 studies presented the results of synbiotic and probiotic interventions, respectively. After intervention, the durations of diarrhea (weighted mean difference (WMD) = -16.63 [-20.16; -12.51]) and hospitalization (risk ratio (RR) = 0.59 [0.48; 0.73]) were shorter, the stool frequency on day 3 (WMD = -0.98 [-1.55; -0.40]) was decreased, and the incidence of diarrhea lasting 3 days was lower in the probiotic and synbiotic groups than in the control groups. Furthermore, in the subgroup analyses, synbiotics were more effective than probiotics at reducing the durations of diarrhea and hospitalization, and Saccharomyces and Bifidobacterium were more effective than Lactobacillus at reducing the duration of diarrhea. CONCLUSION: This meta-analysis supports the potential beneficial roles of probiotics and synbiotics for AD in children. Further research is needed to determine problems associated with probiotic/synbiotic mixtures and appropriate dosages.