We report a rare case of inflammatory pseudotumor arising in the submandibular gland, which presented with autoimmune disease-like clinical manifestations. A 70-year-old Japanese man developed masses in both submandibular regions. Laboratory tests revealed polyclonal hypergammaglobulinemia, high titers of antinuclear antibody, and a positive thyroid test. Histologically, the lesion was composed of multiple nodules separated by thick fibrous bands and contained a few atrophic lymphoid follicles and residual ductal structures. At higher magnification, the nodules contained numerous mature plasma cells mixed with myofibroblasts, lymphocytes, and histiocytes. Occasionally, the myofibroblasts were arranged in poorly formed fascicles and in a storiform pattern. Polymerase chain reaction analysis failed to demonstrated the rearrangement of the immunoglobulin heavy-chain gene. The patient was free of disease after 72 months follow-up. Marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type arising from salivary glands occasionally showed prominent plasma cell differentiation. The present case indicates that inflammatory pseudotumor should be added to the list of different diagnoses for mucosa-associated lymphoid tissue-type lymphoma of the salivary glands.