Lymphoma is the most common hematopoietic malignancy in dogs. Diagnosis of lymphoma is classically performed by morphological assessment and immunohistochemistry. But some cases in the early stage are difficult to distinguish and need more objective and accurate methods. So, Polymerase chain reaction (PCR) for antigen receptor rearrangements (PARR) and flow cytometric immunophenotype of lymphoma have been developed continuously. In this study, we performed these two methods to classify lymphoma type in 3 cases. According to PARR analysis, B cell origin lymphoma was diagnosed in two of three cases by testing PBMC and lymph node. All fine needle aspiration (FNA) samples of lymph nodes had high expression of CD21 on >88% of total cell population and PBMC samples also showed high expression of CD21 on >30% of total lymphocytes in those two cases, while the expression of CD3, CD4 and CD8 was absent. These results suggest that concurrent use of PARR and flow cytometric immunophenotype is more effective and valuable tool for the diagnosis and monitoring of canine lymphoma patients.