Background and Aims: Removal/suppression of the primary etiological factor reduces the risk of decompensation and mortality in compensated cirrhosis. However, in decompensated cirrhosis, the impact of etiologic treatment is less predictable. We aimed to evaluate the impact of etiological treatment in patients with cirrhosis who developed ascites as single index decompensating event. Approach and Results: Patients with cirrhosis and ascites as single first decompensation event were included and followed until death, liver transplantation, or Q3/2021. The etiology was considered “cured” (alcohol abstinence, hepatitis C cure, and hepatitis B suppression) versus “controlled” (partial removal of etiologic factors) versus “uncontrolled.” A total of 622 patients were included in the study. Etiology was “cured” in 146 patients (24%), “controlled” in 170 (27%), and “uncontrolled” in 306 (49%). During follow-up, 350 patients (56%) developed further decompensation. In multivariable analysis (adjusted for age, sex, varices, etiology, Child-Pugh class, creatinine, sodium, and era of decompensation), etiological cure was independently associated with a lower risk of further decompensation (HR: 0.46; p = 0.001). During follow-up, 250 patients (40.2%) died, while 104 (16.7%) underwent LT. In multivariable analysis, etiological cure was independently associated with a lower mortality risk (HR: 0.35, p < 0.001). Conclusions: In patients with cirrhosis and ascites as single first decompensating event, the cure of liver disease etiology represents a main treatment goal since this translates into considerably lower risks of further decompensation and mortality.