A population of the large-scaled goby Thorogobius macrolepis (Kolombatovic, 1891) is described from the Bay of Rijeka, Croatia, north-eastern Adriatic Sea. Known to date only from three specimens, the discovery of the population of this small Gobiidae species permits the description of the variation of body proportions and of the head lateral-line system, the coloration in life, the sexual dimorphism, and also biological and ecological aspects. Data on the morphometrics, meristics and papillae counts are given. T. macrolepis is an epibenthic inshore species. It occurs on sandy substrate near crevices with vertical rock faces, from 6 to 42 m. Maximum SL is 52.6 mm in females, 54.8 mm in males. The urogenital papillae are of typical gobiid pattern and are developed in their characteristic shape for males and females at a size exceeding 28.5 mm SL.