Acute-on-chronic liver failure (ACLF) is a clinical condition of abrupt hepatic decompensation in chronic liver disease patients that is associated with extra-hepatic organ failures and a higher mortality rate. This study aimed to identify the clinical patterns and outcomes in cirrhotic Yemeni patients with ACLF. This prospective cohort study was carried out on 160 cirrhotic patients admitted between May 2023 and May 2024 to the Internal Medicine Department in Al-Sadaqah General Teaching Hospital in Aden governorate, Yemen. Based on the European Association for Study of Liver's Chronic Liver Failure Consortium EASL-CLIF criteria, patients were divided into Group A: 54 patients with ACLF. Group B: 106 patients without ACLF. The prevalence of ACLF is 33.8%. The mean age was 41.54± 8.11 years in ACLF and 39.22± 8.14 years in non-ACLF patients. The proportion of males in ACLF was 51.9% vs. 57.5% in non-ACLF patients. The most common causes of cirrhosis were cryptogenic (58.8%) and autoimmune hepatitis (25.6%). A significant correlation was found between prior hospitalization, decompensation, and the increased risk of developing ACLF. The most common complications were jaundice, hepatic encephalopathy, renal failure, signs of bacterial infection, ascites, and gastrointestinal bleeding, respectively. The main precipitating events for ACLF were bacterial infection, especially SBP (48.1%), GIT bleeding (24.1%), and no identified precipitating events (24.1%). The most common organ failures were renal (70.4%), liver (42.6%), and cerebral (31.5%). ACLF patients showed higher levels of WBCs, bilirubin, and serum creatinine. Mortality rates were significantly higher in ACLF patients compared to non-ACLF at both 28 days (33.3% vs. 5.7%) and 90 days (685% vs. 23.6%). This study demonstrated that ACLF patients have worse prognoses, higher mortality rates, increased ICU admission, lower survival, and higher rates of organ failure than non-ACLF patients.