Purpose The optimal timing of elective surgery in patients with the colonic diverticular disease remains controversial. We aimed to analyze the timing of sigmoidectomy in patients with diverticular disease and its influence on postoperative course with respect to the classification of diverticular disease (CDD). Methods Patients who underwent elective laparoscopic sigmoidectomy were retrospectively enrolled and subdivided into two groups based on the time interval between the last attack and surgery: group A, early elective (≤ 6 weeks), and group B, elective (> 6 weeks). Multivariate regression models were used to identify factors which predict conversion to laparotomy, postoperative course, and length of hospital stay. Results A total of 133 patients (group A (n = 88), group B (n = 45)) were included. Basic demographic data did not differ between groups except for a higher rate of diabetes in group B (p = 0.009). The conversion rate was significantly higher in group A in comparison to group B (group A vs. group B: n = 23 (26.1%) vs. n = 3 (6.7%), p = 0.007). Logistic regression analysis revealed the timing of surgery and CDD stage as significant predictors for intraoperative conversion. Moreover, the postoperative course was influenced by high age as well as intraoperative conversion and length of hospital stay by conversion, preoperative CRP levels, and elective surgery. Conclusions Both, timing of surgery and the disease stage, influence the conversion rates in laparoscopic sigmoidectomy for diverticular disease. Accordingly, patients with complicated acute or chronic sigmoid diverticulitis should be operated in the inflammation-free interval.