Granulomatous slack skin is a rare variant of indolent cutaneous lymphoma, characterized by a cutis laxa-like clinical appearance and widespread granulomatous infiltration. A 25-year-old man had suffered from slowly progressive infiltrative, scaly and atrophic plaques and flaccid nodules with deep induration in the axillae, trunk and thighs. Histopathologically, dense lymphoid cell infiltration with numerous multinucleated giant cells (MGC) throughout the dermis to the subcutaneous tissue was observed. T-cell receptor gene rearrangement was detected in the skin lesions. Granulomatous infiltration with MGC was found in enlarged lymph nodes and the liver. Acute exacerbation was successfully treated with systemic recombinant interferon-gamma.