In this study, socio-economical structure of the Marmara Sea (Istanbul) coastal fishermen who are members of fishery co-operatives was investigated. For this purpose, fifty fishery co-oper-atives which of fifteen located in Anatolian Side of Marmara Sea were analyzed. The county center where the fishery co-operatives affiliated were visited to determine the number of members and the boats and also during 2007-2008 fishing season at different times the ques-tionnaire forms were filled out face to face with fishermen. According to the results obtained, length of fishing boats varied between 6.00 to 9.00 meter and all of them were motorized. Fi-shermen ages ranged between 29-83 and among them 2.6 % were literate, 41.7% graduated from primary school, 20.0% from secondary school, 27.0% from high school and 8.7% from university. 21-30 years of professional experience in fishing had the highest ratio with 29.6% and 62.6% of them did only fishing line, 37.4% net-fishing line 44.3% of fishermen’s income originated only from fishing and 55.7% did fishing to support family budget with an extra in-come. 80.9% of fishermen had a social security and 65.2% of them had their own houses. As a result, it can be said that in investigated area co-operatives and fisherman did not keep records sufficiently, they had low incomes and the marketing organizations were not sufficient.