The authors report 2 cases of sea urchin granuloma of the nail apparatus resulting in permanent nail deformity. Both patients developed periungual and subungual nodular lesions 1–2 months after sea urchin spine injuries in the Mediterranean sea. The affected nails showed periungual nodules associated with splitting of the nail plate distal to the nodules. Surgical excision of the nail lesions required the removal of a large amount of nail matrix that resulted in permanent nail plate dystrophy. Histopathology revealed typical foreign-body granulomas in the nail dermis.