Background/Aims: We aimed to investigate the differences in direct healthcare costs between patients with and without inflammatory bowel disease (IBD) and changes in direct healthcare costs before and after IBD diagnosis. Methods: This population-based study identified 34,167 patients with IBD (11,014 patients with Crohn's disease and 23,153 patients with ulcerative colitis) and 102,501 age-and sex-matched subjects without IBD (the control group) from the National Health Insurance database using the International Classification of Disease, 10th revision codes and the rare intractable disease registration program codes. The mean healthcare costs per patient were analyzed for 3 years before and after IBD diagnosis, with follow-up data available until 2015. Results: Total direct healthcare costs increased and peaked at $2,396 during the first year after IBD diagnosis, but subsequently dropped sharply to $1,478 during the second year after diagnosis. Total healthcare costs were higher for the IBD patients than for the control group, even in the third year before the diagnosis ($497 vs $402, p<0.001). The costs for biologics for the treatment of IBD increased steeply over time, rising from $720.8 in the first year after diagnosis to $1,249.6 in the third year after diagnosis (p<0.001). Conclusions: IBD patients incurred the highest direct healthcare costs during the first year after diagnosis. IBD patients had higher costs than the control group even before diagnosis. The cost of biologics increased steeply over time, and it can be assumed that biologics could be the main driver of costs during the early period after IBD diagnosis.