Taking into account the polyethnic nature of Ukrainian society, it is important to study the history of ethnic minorities in Ukraine, among which a meaningful place is occupied by Bulgarian minority. It has several historically formed areas of compact settlement in the South of Ukraine, and this had caused certain peculiar regional features of its ethnocultural development. In this paper, we aim to identify the factors that influenced the ethnocultural development of Bulgarian ethnic minority during 1943-1991 in one of the areas of its compact settlement – in the North Azov Sea region. The lower chronological limit is the moment of liberation of the region from Nazi invaders and the restoration of Soviet power with its ethnopolitics, and the upper one is the collapse of the Soviet Union, which led to a qualitatively new period in national history. The influence of a number of internal and external factors on the ethnocultural development of the Bulgarian ethnic minority in the North Azov Sea region is analyzed. Among these factors were the quantitative composition of the ethnic minority, the presence of the institutions that assisted in strengthening ties in its environment, national policy of the state, the possibility of cultural links of the ethnic minority with the core of its ethnic group outside the country of residence (the so-called historical homeland), and the status of interethnic relations at the regional and national levels. At the beginning of the analyzed period, the total number and characteristics of the settlement (mostly compact settlement) played a favorable role in the ethnocultural self-reproduction of the studied ethnic group. Over time, the number of the members of Bulgarian minority in the region began to decline, and the characteristics of the settlement changed to a mixed compactly dispersed, intensifying the assimilation processes. Free ethnocultural development was impeded by the low institutional fullness of Bulgarian ethnic group in the North Azov Sea region, artificially caused by political influence: Bulgarians in the region lacked national education and media. State policy, which was highly discriminatory at the beginning of the studied period, changed to moderately discriminatory from the mid-1950s, and that improved the situation of the Bulgarian ethnic minority. The peaceful nature of interethnic relations had a similar effect. Although there was no direct prohibition on keeping relations with the historical homeland, the Bulgarians of the Azov Sea region had limited opportunities in this regard, unlike the Bulgarians of Bessarabia region. This contributed to the preservation of archaic cultural features, the marginalization of Bulgarian culture. As the result of the study, it has been found out that the combined effect of the above-mentioned factors caused a general vector of influence on the ethnocultural development of the Bulgarian ethnic minority in the North Azov Sea region towards the gradual partial assimilation.