<b>Abstract</b>— <p>Until recently, the Kara Sea was a relatively stable ecosystem unaffected by alien species, but in the early 21st century, the Arctic shelf was invaded by the snow crab <i>Chionoecetes opilio</i>. This predator has a wide dietary range and can feed on echinoderms, especially ophiuras, mollusks, polychaetes, and crustaceans. This article reports data on the study of benthic communities of the southwestern Kara Sea, based on the materials collected in 2014 and 2019 (before and after the mass appearance of the snow crab). The period of 2014–2019 was marked by significant changes in the structure of benthic communities, while abiotic parameters (near-bottom temperature, salinity, and sediment characteristics) remained almost constant at the investigated stations. The most significant changes affected the megafauna. The total megabenthos abundance and biomass decreased, the abundance of dominant species also reduced, and the species structure became more even. Most likely, the observed transformation of the benthic communities is related to the establishment of the snow crab, the most affected were dominant benthic species which are the main prey items of this crab.</p>