In this study, a new Aleocharinae Fleming, 1821 (Coleoptera: Staphylinidae) species, Leptusa (Roubaliusa) giresunensis sp. n. (Coleoptera: Staphylinidae: Aleocharinae), is described from Giresun Province in Turkey. The study was conducted between March 2013 and March 2016 in the Eastern Black Sea Region and new species was collected in 2014-2015. Photographs of the habitus are given and antenna, aedeagus, spermatheca, and both male and female sternite VII-VIII and tergite VIII are illustrated for the new species. Furthermore, species list of the Leptusa for Turkey, identification key and maps of the new species and congeners are given. The habitus, aedeagus and spermatheca are distinguished from similar species Leptusa trapezuntis Pace, 1989 and Leptusa flagrifera Assing, 2009 (Coleoptera: Staphylinidae: Aleocharinae).