Background and aim: Extensive epidemiological evidence suggests that nonalcoholic fatty liver disease (NAFLD) is the primary chronic liver disease worldwide. However, some studies have showed conflicting results on the effects of probiotics and synbiotics supplementation. Therefore, we conducted a systematic review and meta-analysis to investigate the effectiveness of the supplementation in subjects with NAFLD. Methods: We searched systematically PubMed, Cochrane, and Embase databases up to April 2018 and checked manually the bibliography of the original articles. The quality of the studies was evaluated using the Cochrane Risk of Bias Tool. Results: This study analyzed 15 randomized, controlled trials involving 782 patients with NAFLD. Probiotics and synbiotics supplementation could significantly improve liver steatosis, alanine aminotransferase, aspartate aminotransferase, triglyceride, total cholesterol, high-density lipoprotein, low-density lipoprotein, homeostasis model assessment-insulin resistance, liver stiffness and tumor necrosis factor-alpha (all P < 0.05). But the supplementation could not ameliorate body mass index (mean difference [MD] = -0.00; 95% confidence interval [CI]: -0.22 to 0.22, P = 0.99), waist circumference (MD = -0.01; 95% CI -0.03 to 0.02, P = 0.57) and fasting blood sugar (standard mean difference [SMD] = -0.10; 95% CI -0.32 to 0.12, P = 0.39). Conclusion: We present clear evidence for the benefit of probiotics and synbiotics supplementation for liver steatosis, liver enzymes, lipid profiles and liver stiffness in patients with NAFLD. Keywords: Meta-analysis; Nonalcoholic fatty liver disease; Probiotics; Synbiotics.