Background/AimsInflammatory bowel disease (IBD) may contribute to the development of hematologic malignancies. In this study, the potential relationship between IBD and hematologic malignancies was investigated.MethodsWe searched the PubMed, Web of Science, Embase, and Cochrane Library databases for all cohort studies comparing the incidence of hematologic malignancies in non-IBD populations with that in IBD patients, and we extracted relevant data from January 2000 to June 2023 for meta-analysis.ResultsTwenty cohort studies involving 756,377 participants were included in this study. The results showed that compared with the non-IBD cohort, the incidence of hematologic malignancies in the IBD cohort was higher (standardized incidence ratio [SIR]=3.05, p<0.001). According to the specific types of IBD, compared with the non-IBD patients, the incidences of hematologic malignancies in ulcerative colitis patients (SIR=2.29, p=0.05) and Crohn's disease patients (SIR=3.56, p=0.005) were all higher. In the subgroup analysis of hematologic malignancy types, compared with the control group, the incidences of non-Hodgkin's lymphoma (SIR=1.70, p=0.01), Hodgkin's lymphoma (SIR=3.47, p=0.002), and leukemia (SIR=3.69, p<0.001) were all higher in the IBD cohort.ConclusionsThe incidence of hematologic malignancies, including non-Hodgkin's lymphoma, Hodgkin's lymphoma, and leukemia is higher in patients with IBD (ulcerative colitis or Crohn's disease) than in non-IBD patients.