The focus of the present study was to provide information on European hake gillnet fishery in the southern Sea of Marmara (Turkey) based on samples collected during in high fishery season between April and May 2013 with experimental gillnets of different mesh sizes. European hake gillnets of three mesh sizes 28, 30, and 32 mm (nominal bar length) were set at between the 50 and 70 m depth water to test the effects of mesh size on the species composition, size of fish, catch rates, catch composition, bycatch and discard ratios and CPUE estimates. Cluster analysis was used to examine the stability of the results. Multi-dimensional scaling (MDS) was also applied to assess catch species aggregation patterns in the catch. The results showed that, 1062 specimens (182.79 kg) belonging to 8 species were caught and Merluccius merluccius and Solea solea were two dominant species of the catches with all studied mesh sizes with the percentage of 76.57, 19.54% in biomass and 48.96, 39.36% in number of specimens, respectively. The size frequency distribution of M. merluccius and S. solea are determined with the length range of 23.5 to 41.0 cm TL (mean 31.9 +/- 0.14 cm) and 18.5 to 35.5 cm TL (mean 22.2 +/- 0.09), respectively. The highest CPUE estimates by number and biomass of European hake was determined in 30 mm mesh size as 0.093 n.m(-1) and 25.153 g.m(-1), respectively. The similarity levels found by cluster analyses indicated that 32 mm mesh size is different from 28 and 30 mm mesh size with 85.67 and 85.55% respectively, for number of specimens and biomass based on standardized data. Since the present study reported here is the first concerning European hake gillnet fisheries and these findings will help to improve the management and conservation of this fishery.