A 12-year-old spayed female toy poodle with gastrointestinal symptoms was presented to the primary care veterinarian.Based on laboratory findings, she was diagnosed with pyelonephritis and post-renal renal failure associated with distal ureteral swelling. The dog underwent partial ureteral resection and ureterobladder neoanastomosis for definitive pathological diagnosis and treatment of the ureteral swelling. The dog was diagnosed with extranodal peripheral T-cell lymphoma based on histopathology, immunostaining, and lymphocyte clonality studies. To our knowledge, this is the first report of canine primary ureteral lymphoma. This case highlights that primary ureteral lymphoma should be considered in the differential diagnosis of primary ureteral tumors in dogs. Further case series are needed to determine the prognosis and establish treatment options.