In order to determine the tintinnid species and abun-dance in the Gulf of Gemlik and some ecological variables that affect the distribution of the species, samples were collected with a Ruttner bottle and a plankton net (40 µm) at 11 stations (6 shore, 5 offshore) between in June 2010 and May 2011 monthly. The examination of the samples, 28 tintinnid species belong to 7 familia, 12 genera were identified. According to the literature information, 18 spe-cies were new entries for the Marmara Sea, and 4 of them were also new entries for the Turkish coastal waters (Eutin-tinnus medius (Kofoid and Campbell) Kofoid and Camp-bell, 1939, Metacylis mediterranea (Mereschkowsky) Jör-gensen, 1924, Tintinnopsis acuminata Daday, 1887 and Tintinnopsis urnula Meunier, 1910). The majority of the species composition was represented with Codonellidae and Tintinnidae families (both of them had 8 species, 28.6 %). The genus Tintinnopsis were observed as dominant when compare with the others according to numbers of individuals. Primary hydrographic conditions such as temperature (8.1-29.3 ºC), salinity (14.98-38.65 ppt), dissolved oxygen (2.06-17.18 mg l -1), and pH (7.7-8.8) were recorded maximum and minimum values at each sampling station.