Background and Aims Given the paucity of population-based data on the association between inflammatory bowel diseases (IBD), celiac disease (CeD) and celiac autoimmunity (CeA) we aimed to study the associations in a nationwide study. Methods Utilizing health administrative data for all four health maintenance organizations in Israel, covering 98% of the population, we explored the prevalence of CeD in children and adults with IBD versus non-IBD matched controls. CeD was defined by three ICD-9 codes and CeA by positivity for tissue transglutaminase antibodies. Results In total, 34,375 IBD patients (56% Crohn's disease [CD] and 44% ulcerative colitis [UC]) were compared with 93,603 non-IBD controls. Among IBD patients, 319 (0.93%) had CeD versus 294 (0.31%) non-IBD controls (odds ratio [OR]=2.97 [95%CI 2.54-3.48]; p<0.001). CeA was identified in 575 (1.67%) IBD patients vs. 158 (0.17%) controls (OR=10.06 [95%CI 8.43-12], p<0.001). The prevalence of CeD was higher in pediatric-onset IBD (87/5,243 [1.66%]) than adult-onset IBD (232/29,132 [0.79%]; p<0.001). CD patients had a higher prevalence of CeD (229/19,264 [1.19%]) than UC patients (90/15,111 [0.56%]; OR=2.01 [95%CI 1.57-2.56]; p<0.001). The diagnosis of CeD preceded the diagnosis of IBD in 241/319 cases (76%). The time to treatment escalation was shorter in patients with both IBD and CeD than in patients with IBD without CeD (p=0.017). Conclusion CeD and CeA are more prevalent in IBD patients, especially in pediatric-onset IBD and in CD. The diagnosis of CeD usually precedes that of IBD. Having CeD is associated with more intensified treatment for IBD.