Background: Acute pancreatitis (AP) and metabolic syndrome (MetS) are common clinical problems with serious complications and high cost of treatment. The relationship between MetS and severity of AP is unknown, and because there are very few published articles, further studies had been recommended. Therefore, we designed this study to estimate the association between MetS and its components with AP severity. Patients and Methods: In this prospective analytical cross-sectional study, all AP patients who referred to two referral hospitals affiliated with Shiraz University of Medical Sciences between 2016 and 2019 were evaluated. The diagnosis of MetS syndrome as well as follow-up of patients for evaluation of severity and outcome of AP was performed in all enrolled patients. National Cholesterol Education Program Adult Treatment Panel III (NCEP/ATP-III) was used for diagnosis of MetS. Bedside Index for Severity in Acute Pancreatitis (BISAP) and revised Atlanta classification (RAC) were used to estimate the severity of AP. Finally, the association between MetS syndrome and its components at different AP severities was compared. Results: Of the 214 patients referred to our center, a total of 76 patients with AP were included in this study. Of the included patients, 40 (52.6%) were male and 36 (47.4%) were female. Frequency of patients in Mets and non-MetS groups was 34 (44.74%) and 42 (55.26%), respectively. The gender and mean age difference between Mets and non-MetS groups were not statistically significant. According to Mets groups, 25 (73.5%) and 9 (26.5%) AP patients with MetS had BISAP score of 0-2 and 3-5, respectively. BISAP score in MetS group was significantly higher than non-MetS group (P = 0.022). Overall, 20 (58.8%), 11 (32.4%), and 3 (8.8%) of AP patients with MetS had mild, moderately severe, and severe AP based on RAC, respectively. Severe RAC was significantly higher in the MetS group than in the non-MetS group (P = 0.029). The frequency of complications in MetS group was significantly higher than in non-MetS group (P= 0.008). The length of hospital stay was also significantly higher in the MetS group than in the non-MetS group (P = 0.001). Overall, three patients died, two of whom had MetS and all had severe RAC and BISAP 3-5. Waist circumference, fasting blood sugar, and triglyceride were significantly higher in the severe and moderately severe types of AP group than in the mild AP group, according to RAC. Although, mean of all components of MetS except HDL-cholesterol were higher in BISAP of 3-5 group than BISAP of 0-2 group, the difference was only significant in waist circumference. Conclusion: The present study showed that there was a significant association between the rate of MetS and its components including waist circumference, hyperglycemia and hypertriglyceridemia with increasing AP severity. This study showed that the incidence of more severe AP in patients with MetS is much higher than in patients without MetS. We recommend that the new studies with larger sample sizes are conducted wit...