Objective: To investigate whether insulin resistance (IR) affects the prognosis in patients with diffuse large B-cell lymphoma (DLBCL).Place and Duration of the Study: The Fourth Hospital of Hebei Medical University, Shijiazhuang, China, from September 2017 to December 2021.Methodology: This study retrospectively analysed 324 patients with DLBCL who were divided into a non-IR group (251 cases) and IR group (73 cases) according to IR. The authors collected clinical data of the study population and calculated the overall survival (OS) of patients through inpatient case data or follow-up. The Cox regression method was used to assess the prog-nostic factors of the patients. The Kaplan-Meier method was used for drawing the survival curve of IR on OS of the DLBCL patients.Results: The IR group had older age, higher international prognostic index (IPI), later stage, and higher insulin levels. The five-year OS rate was 46% in the IR group and 66% in the non-IR group. Compared with the non-IR group, the IR group showed a poor prognosis (OS: adjusted HR 1.23, 95% CI: 1.02-1.41, p = 0.031).Conclusion: IR was one of the factors leading to poor prognosis in patients with DLBCL, and attention should be paid to this risk factor.