A 53-year-old man presented with asymptomatic, dusky reddish nodules on his trunk, which had persisted for 7 years. Histological findings showed nodular to diffuse dermal infiltration of lymphocytes with irregular nuclei, eosinophils, plasma cells, and mast cells. CD20 revealed patch positivity. Periphery of lymphoid follicles showed BCL-2 positivity and BCL-6 positivity focally at the center. CD30 and toluidine blue staining showed positivity, and several mast cells were confirmed. The immunoglobulin heavy chain gene rearrangement result showed B-cell monoclonality. The patient's condition was diagnosed as cutaneous marginal zone B-cell lymphoma, plasmacytoid type with mastocytosis. Primary cutaneous marginal zone B-cell lymphoma is an indolent lymphoma with a tendency for local recurrence. In the specimen obtained from our patient, multiple mast cells were observed. Primary cutaneous marginal zone B-cell lymphoma with prominent mastocytosis is rare and there are a few reported cases. Therefore, this case is worth reporting for its rarity and for the purpose of reminding mastocytosis in primary cutaneous marginal zone B-cell lymphoma.