A new species of entomopathogenic nematode (EPN), [i]Steinernema tbilisiensis sp. n.[/i] is described. The species was isolated from soil samples of the deciduous forest located in the Tbilisi area. Morphological and morphometric data as well as phylogenetic analysis show that [i]S. tbilisiensis sp. n.[/i] belongs to the group S. affine/intermedium. [i]S. tbilisiensis sp. n.[/i] has been attributed to the group [i]S. affine/intermedium[/i] on the basis of spicule and gubernaculum structure. The new species differs from other species of the [i]S.affine/intermedium[/i] group in the following diagnostic characters: the spicule of [i]S. tbilisiensis sp. n.[/i] is the smallest and the gubernaculum of [i]S. tbilisiensis sp. n.[/i] is shorter than other species of the [i]S. affine/intermedium[/i] group. Infective juveniles (IJs) of [i]S. tbilisiensis sp. n.[/i] are distinguished by a relatively long body (L = 866 μm), the position of excretory pore (EP = 72 μm), the length of the esophagus (ES = 140 μm) and the length of the anal body width (ABW = 25 μm). IJs of [i]S. tbilisiensis sp. n.[/i] have four lateral lines like [i]S. beddingi[/i], but the number of lines is six in [i]S. affine[/i], [i]S. sichuanense[/i] and [i]S. intermedium[/i]. Also the analysis of rDNA (28S and ITS) gene sequences depicts this Steinernema species as a distinct and unique entity.