The aim of this research was to find out the amount of melanomacrophage centres (MMC) in liver and kidney of nile tilapia (Oreochromis niloticus) fish reared in high dense population. Fifty nile tilapia were grouped in four treatment groups, group I contain 5 fish, group II contain 10 fish, group III contain 15 fish and group IV contain 20 fish. Treatment was carried out for 24 hours. Fish was necropsied to collect the liver and kidney, fixed in NBF 10% then proceed to histopathological method using hematoxilin and eosin for staining. Histopathological observation was done microscopically, and MMC was captured by photomicrograph. The data were analyzed descriptively. The result showed that the average of MMC number in fish liver in group K1, K2, K3, and K4 were 9.6, 11.3, 12.6, and 13.2. While the average of MMC number in fish kidney were 5.5, 7.7, 8.5, and 9.2, respectively. The higher the dense of population the higher the amount of MMC found in liver and kidney of nile tilapia.