Purpose: Colonic diverticulosis and abdominal wall hernia are common pathologies. Studies have suggested that connective tissue alterations play a role in the formation of both diverticulosis and abdominal wall hernia. The aim of this cohort study was to evaluate the association between diverticulosis and abdominal wall hernia in a large cohort of patients undergoing colonoscopy. Methods: All consecutive patients who underwent colonoscopy between 2001 and 2013 at Bispebjerg Hospital were eligible for inclusion. The endoscopists prospectively registered the findings of diverticulosis in a database. Data were merged with the Danish Hernia Database identifying patients who underwent groin and ventral hernia repair. Calculated odds ratios (ORs) were used to describe the extent of association and multivariable logistic regression models were utilized to adjust for age and gender. Results: A total of 13,855 patients were included, 3685 (26.6%) of whom were diagnosed with diverticulosis. Diverticulosis was independently associated with direct inguinal, OR 1.33, 95% CI 1.00–1.76, P = 0.049, and umbilical/epigastric hernia repair, OR 1.74, 95% CI 1.16–2.63, P = 0.008. Conclusions: Colonic diverticulosis was associated with direct inguinal and umbilical/epigastric hernia repair suggesting that connective tissue alterations, herniosis, could be a common etiologic factor of colonic diverticulosis and these abdominal wall hernias.