Background <p>This meta-analysis aims to systematically review and summarize epidemiological evidence regarding the bidirectional association between asthma and IBD.</p> Methods <p>We performed a meta-analysis using data from PubMed, Embase, and the Cochrane Library, with searches conducted up to September 3, 2024. Observational studies examining the association between asthma and IBD were included. The risk of bias was assessed using the Newcastle–Ottawa Quality Assessment Scale (NOS). Pooled OR with 95% CI were calculated using a random-effects model.</p> Results <p>Our analysis included 20 studies with 14,976,781 participants. The risk of IBD among asthma patients was found to be elevated (OR = 1.33, 95% CI 1.19–1.48). Conversely, IBD patients had a higher risk of developing asthma (OR = 1.32, 95% CI 1.12–1.55). Subgroup analysis revealed that asthma was associated with an increased risk of Crohn’s disease (CD) (OR = 1.32, 95% CI 1.12–1.55), but not ulcerative colitis (UC) (P = 0.099). The risk of asthma was higher in patients with CD (OR = 1.25, 95% CI 1.01–1.54) and UC (OR = 1.49, 95% CI 1.20–1.53).</p> Conclusions <p>This meta-analysis identifies a bidirectional association between asthma and IBD, highlighting a significantly increased risk for both conditions. Clinicians should be aware of this relationship to better manage and monitor patients with either disease.</p> <p><i>Trial registration</i> Registration number CRD42024586171</p>