A 9 year old male castrated mixed breed dog presented to the Cornell University Hospital for Animal’s Emergency Service for evaluation of one week duration of enlarged peripheral lymph nodes and increased respiratory efforts while sleeping. Lymphoma was presumptively diagnosed on clinical signs and right mandibular lymph node cytology. Additional diagnostics (bloodwork, thoracic radiographs, abdominal ultrasound, bone marrow aspirate, and lymph node biopsy) were performed to further diagnose and stage the dog; results indicated stage IIIb T-cell lymphoma with a humoral hypercalcemia of malignancy (HHM). This paper will discuss the prognostic factors used to classify a patient with lymphoma as well as present the paraneoplastic condition of HHM that have been associated with this disease. Another topic in this paper will be the use of a multi-agent chemotherapy treatment (CHOP-based protocol) for our patient.