Background: IBD diagnosed after the age of 60 is increasing. Data on post-operative complications in elderly onset IBD are scarce. Aim: To describe the incidence of and factors associated with post-operative complications in elderly onset IBD, diagnosed after the age of 60. Methods: Using EPIMAD Cohort (1988-2006), among 841 incident IBD patients, 139 (17%) underwent intestinal surgery, including 100 Crohn's disease (CD) and 39 ulcerative colitis (UC). Results: After a median post-operative follow-up of 6 years (2-10), 50 (36%) patients experienced at least 1 complication with a total of 69. During the first 30 post-operative days, the mortality rate was 4%. Thirty-two early complications (<30 days) were observed in 23 patients (17%), with 15 infectious, without significant difference between CD and UC. More than half early post-operative complications (n = 19, 59%) were severe (>grade 2) without significant difference between CD and UC (P = 0.28). Thirty-seven long-term adverse effects of surgical therapy (≥30 days) were observed in 33 patients (24%). Multivariate analysis found (1) acute severe colitis (OR = 7.84 [2.15-28.52]) and emergency surgery (OR = 4.46 [1.75-11.36]) were associated with early post-operative complications, and (2) Female gender (HR = 2.10 [1.01-4.37]) and delay before surgery >3 months (HR = 2.09 [1.01-4.31]) with long-term adverse effects of surgical therapy. Conclusions: One-third of elderly IBD patients experienced at least 1 post-operative complication. Half of the early complications were severe, and infectious. Emergency surgery was the key driver for post-operative complication.