The article aims to examine the participation of the Greek merchant fleet in the navigation of the Black and Azov Seas in the mid-nineteenth century on the basis of a complex of Austrian sources that has been little studied in Ukrainian historiography. The latter included published reports from Austrian consular offices in Odesa, Berdiansk, Mariupol, Trebizond, and Galați. Materials from the Austrian press of the time are also used, primarily from the Austrian Ministry of Commerce's “Austria” newspaper, which was published as a daily newspaper from 1849 to 1856 and as a weekly from 1856. During the period under review, the Greek fleet was in a leading position in shipping in the Black and Azov Seas, successfully competing with the Austrian, British and Italian fleets. The success of the Greek merchant fleet was due, among other things, to the fact that seafaring was an ancient Greek craft, and in Ottoman times they were able to maintain the continuity of experience and tradition. In addition, this was facilitated by the developed network of Greek trading houses, which were widely represented in the main area of their fleet's navigation, in the Mediterranean Sea, especially its eastern part, and in the Black and Azov Seas. Therefore, the radical political and economic changes in the Black and Azov Seas regions did not take them and the Italians by surprise, and they were the first to take advantage of the rapid development of trade and transport traffic there. And despite increased competition in the mid-nineteenth century from the Austrians and the British, the Greeks continued to hold top positions in the shipping of the Black and Azov Seas. Moreover, unlike the Sardinians, they were gradually involved in long-distance voyages beyond Gibraltar, mainly to Great Britain. At the same time, the challenges for the traditionally sailing Greek merchant fleet from the emergence of steamship lines on the Black Sea were outlined. The first indicators were the activities of some of the Greeks' main competitors, the Austrians, in the Danube ports and on the Bulgarian coast, and the British, Austrians and Turks in the Anatolian ports.