Background and aims: Acute uncomplicated diverticulitis (UD) of the left colon is common and mostly benign. Due to controversy over the definition of UD and the lack of adequate follow-up in most studies, good quality data to predict long-term outcomes after a first episode of UD are missing. The aim of this study was to assess the long-term risk for adverse outcomes after a first episode of UD. Methods: All consecutive patients with a CT-scan-documented first episode of acute UD (staged "uncomplicated" according to ESCP guidelines and/or modified Hinchey stages 0-1a, and/or CDD 1-2a) between January 2010 and June 2013 were included in the study. CT scans and clinical records were retrospectively reviewed. The primary endpoint was overall recurrence; the secondary endpoint was surgery for diverticular disease. Results: One hundred and five patients were included in the study with a median follow-up of 116.4 (4.9-154.7) months. Of these, 51 (48.5%) patients had a recurrence, 11 (10.4%) had 4 or more episodes. Twenty-one (20%) patients underwent sigmoidectomy, all in an elective setting, mostly due to multiple recurrent episodes. Male gender was the only independent risk factor for surgery (OR (95%CI): 0.301 (0.109-0.834), p = 0.021). Classification systems did not predict recurrence, but stage CDD 1a was protective for surgery (OR (95%CI): 0.201 (0.042-0.957), p = 0.044). Conclusions: After a decade of follow-up, almost half the patients experienced at least one recurrent episode after UD, higher than previously thought. None of those patients required emergency surgery, but one in five patients, mostly men, underwent elective sigmoidectomy for multiple recurrent episodes.