Sand smelt (Atherina boyeri Risso, 1810), which is an exotic species with invasive character, is the third most caught species in the small-scale fisheries among the inland fisheries in Turkey. The fact that it has become an important source of income for the fishermen with low income due to its export potential has led to the maintenance of its stock recently. In this study, the selectivity of coastal beach seine used in the fishing of the species was investigated. A specially designed coastal beach seine with 10 m codend consisting of 4 different compartments was used in the study. Among the compartments of the codend, which was surrounded by a 6 mm mesh cover, in the codend panels mesh with 9, 12 and 14 mm were used. Field studies were carried out on a monthly basis in 4 different stations of Iznik Lake in 2014. Selectivity data were collected by the covered codend method and analyzed by means of a logistic equation with the maximum likelihood method. A totally 3053 individuals were caught length ranged from 2.6-11.2 cm and weight ranged from 0.11-11.02 g. The mean L-50 values of 14, 12- and 9-mm panels were determined as 6.71, 5.62 and 4.51 cm total length, respectively. It is concluded that 12 mm mesh size panel is suitable for sustainable A. boyeri fishery by beach seine net when considered given by length at first maturity size.