BACKGROUND : Fatty liver (FL) has been positively associated with the risk of acute pancreatitis (AP), but whether FL is associated with the severity of AP remains unknown. To this, a meta-analysis was conducted to assess the effect of FL on severity and outcomes of AP. METHODS : We searched PubMed, EMBASE and the Cochrane library to identify all eligible studies (up to June 2017). We pooled the odds ratios (ORs) or weighted mean differences (WMD) from individual studies using a random-effects model to investigate associations between FL and the prognosis of AP. RESULTS : Four studies were included in the meta-analysis, including a total of 805 patients with fatty liver-related acute pancreatitis (FLAP) and 1026 patients with non fatty liver-related acute pancreatitis (NFLAP). The incidences of moderately severe AP (MSAP) (OR = 2.72, 95%CI: 1.82-4.05, P < 0.001) and severe AP (SAP) (OR = 3.57, 95%CI: 2.06-6.18, P < 0.001) were statistically significantly higher in FLAP group than those in NFLAP group. Taking obesity into consideration, a higher rate of MSAP and SAP were also found in patients with FL, no matter whether they were obese or not. Furthermore, mortality (OR = 4.16, 95%CI: 2.57-6.73, P < 0.001), systemic inflammatory response syndrome (SIRS) (OR = 2.82, 95%CI: 2.3-3.47, P < 0.001) and local complications were also statistically significantly higher in the FLAP group than in NFLAP group. CONCLUSIONS : Fatty liver is associated with the severity of acute pancreatitis.