<b><i>Objective:</i></b> Contrasting results are reported on the clinical course of acute diverticulitis (AD) in the geriatric population. The aim of this study is to compare the AD clinical outcomes between patients aged up to 80 years and those ≥80 years. <b><i>Methods:</i></b> A total of 1,139 patients were enrolled: 276 patients aged ≥80 years were compared with a group of 863 patients aged &#x3c;80 years. The primary outcome was to compare the overall mortality. Secondary outcomes included major complications, in-hospital length of stay (LOS), and need for surgical procedures. <b><i>Results:</i></b> Patients ≥80 years with AD had different clinical presentation compared with younger patients: they had less fever (21.4 vs. 35.2%; <i>p</i> &#x3c; 0.001) and abdominal pain (47.8 vs. 65.6%; <i>p</i> &#x3c; 0.001) rates, but a higher digestive tract bleeding (31.5 vs. 12.3%; <i>p</i> &#x3c; 0.001) and fatigue (12.7 vs. 7.1%; <i>p</i> = 0.004) rates. Median LOS, cumulative major complications, and mortality rates were higher for patients ≥80 years.Multivariate analysis identified age, absence of abdominal pain, and dyspnea at presentation as independent predictors of intrahospital death or major complications. <b><i>Conclusions:</i></b> Patients with AD and age ≥80 years have a higher mortality rate and cumulative major complications as compared with younger patients. Invasive treatments were associated to a poor prognosis in this group.