Background: Work productivity (WP) loss includes absence from work (absenteeism) and productivity loss while working (presenteeism), which leads to high indirect costs in inflammatory bowel disease (IBD). Prior health economic analyses predominantly focused on absenteeism. Here we focus on presenteeism and assess predictors of WP loss, fatigue, and reduced health-related quality of life (HRQL). Methods: Employed IBD patients completed the following surveys: Work Productivity and Activity Impairment, Multidimensional Fatigue Inventory, and Short Inflammatory Bowel Disease Questionnaire. Predictors were assessed using uni- and multivariable regression analyses. Annual costs were calculated using percentages of WP loss, hourly wages, and contract hours. Results: Out of 1590 invited patients, 768 (48%) responded and 510 (32%) were included. Absenteeism, presenteeism, and overall WP loss were reported by 94 (18%), 257 (50%), and 269 (53%) patients, respectively, resulting in mean (SD) annual costs of €1738 (5505), €5478 (8629), and €6597 (9987), respectively. Disease activity and active perianal disease were predictors of WP loss (odds ratio [OR] = 6.6; 95% confidence interval [CI], 3.6-12.1); OR = 3.7; 95% CI, 1.5-8.7). Disease activity and arthralgia were associated with fatigue (OR = 3.6; 95% CI, 1.9-6.8; OR = 1.8; 95% CI, 1.0-3.3)) and reduced HRQL (OR = 10.3; 95% CI, 5.9-17.9; OR = 2.3; 95 % CI, 1.4-3.8). Fatigue was the main reason for absenteeism (56%) and presenteeism (70%). Fatigue and reduced HRQL led to increased costs compared with absence of fatigue and normal HRQL (mean difference = €6630; 95% CI, €4977-€8283, P < 0.01; mean difference = €9575; 95% CI, €7767-€11,384, P < 0.01). Conclusions: Disease activity and disease burden lead to WP loss in approximately half of the employed IBD population, driving indirect costs. Fatigue is the most important reason for WP loss.