Under climate change and increasing anthropogenic pressure, rare species with unique ecosystem functions are particularly vulnerable. One of these species is the chestnut goby Chromogobius quadrivittatus, whose presence in the Black Sea has long been considered occasional. The study aims to specify the range, abundance and ecological peculiarities of this species. For this purpose, underwater observations and captures were carried out from 2012 to 2022 near the Crimean and the Caucasian coasts using the apnoea diving method, photosurvey and artificial habitat traps. Four stationary habitats of the species were recorded in the mentioned area predominantly in rocky and stony biotopes in shallow waters. The populations showed mosaic distribution and significant inter-annual fluctuations in abundance. Maximum abundance was recorded in 2016-2018 in Kazachya Bay (Sevastopol) and was up to 3 individuals per square metre. No such concentrations of the species have been noted since 2020. It is presumably due to increased abundance of the rock bass Serranus scriba. In the Black Sea populations, the size characteristics of fish were close to the maximum known and positive allometry was observed. Fish matured at SL 45.5 mm, and the male-to-female ratio in the sample was 1:1. These findings add to the data on species characteristics of the chestnut goby in the Black Sea and indicate the need for a more accurate assessment of its conservation status given limited information on the population abundance and dynamics.