Background and Clinical Significance: Hematologic malignancies, including diffuse large B-cell lymphoma (DLBCL), have been associated with the development of Guillain–Barré syndrome (GBS). Specifically, treatment with the immunomodulator rituximab, which is used in the backbone of DLBCL treatment, has increasingly been used in this patient population. Case Presentation: We present the case of a man in his 60s with DLBCL who presented to the hospital with the progressive weakness of the bilateral upper and lower extremities within 6 weeks of the completion of treatment including rituximab. The temporal relationship between the completion of rituximab and subsequent polyradiculoneuropathy, as well as a favorable response to intravenous immunoglobulin (IVIG), affirmed the diagnosis of treatment-induced GBS. Conclusions: The increased use of rituximab as part of a standard treatment regimen for hematologic malignancies demonstrates the need for an awareness of a possible association between rituximab and the subsequent paradoxical development of GBS, which will allow for expeditious evaluation for better patient outcomes.