An outbreak of a disease with external body lesions in Picasso triggerfish (Rhinecanthus assasi) and black damselfish (Neoglyphieodon melas) has been observed in the indoor aquarium of NIOF, Hurghada, Egypt. Thirty Picasso triggerfish and thirty-five black damselfish were clinically affected with gross skin lesions. The affected fishes were euthanized for gross, histological and bacteriological examinations. The disease onset started after exposing the fish to catching and indoor rearing stress. Anorexia, erratic swimming and hemorrhagic skin and mouth ulcers and fin rot were the main symptoms and lesions among Picasso triggerfish and black damselfish. Single species of bacteria was isolated from skin ulcer, liver and spleen and was diagnosed as Tenacibaculum maritimus. The gross lesions were irregular shallow erosions and deep ulcers on the dorsal and lateral skin, sometimes on the head, mouth and fins, and occasionally, on the cornea. Histological findings, the hepatic tissue revealed fatty degeneration and focal liquefactive necrosis. Congestion, hemorrhage, hemosidrosis and lymphoid depletion was observed in spleen. The deep skin ulcers characterized by epidermal and muscular necrosis. Picasso triggerfish and black damselfish had lesions similar to those of natural infection and mortality rates of 50 and 60%, respectively in experimental reproduction of the disease. The natural T. maritimus infection in Picasso triggerfish and black damselfish in Red Sea is not only a superficial skin lesion but also a systemic infection.