Waldenstr's Macroglobulinemia (WM) is a clonal disorder of small lymphocytes that show maturation to plasma cells synthesizing IgM. It is the biological activity of IgM protein that determines most of the clinical manifestations of the disease. WM most closely corresponds to lymphoplasmacytic lymphoma or immunocytoma of the REAL classification of lymphoma. Here, we report a case of a 50 year old male with squamous cell carcinoma of buccal mucosa. On routine investigations we found autoagglutination of RBCs; on workup with this feature we had suspicion of Waldenstr's Macroglobulinemia. The diagnosis of WM was established after cytomorphology and immunohistochemistry (IHC) analysis of the bone marrow which revealed the presence of a lymphoid/lymphoplasmacytoid-like bone marrow infiltrate along with an elevated serum IgM level. Waldenstr's Macroglobulinemia and its co-existence with autoimmune diseases and non hematological malignancies has already been described in the literature, but the present case was asymptomatic for WM with carcinoma of buccal mucosa, which is the first case reported so far.