The article discusses the causes of illegal emigration of the Mennonites from the Black Sea region, identifies the main routes and shows the role of Mennonite mutual aid in the implementation in the 1920s-1930s. Mennonite memoirs show that the main causes of emigration were repressions against the wealthy layers of the village, the anti-religious struggle that affected wide circles of Mennonites. Young Mennonites suffered from the inability to obtain a higher or secondary specialized education, while maintaining their religious beliefs; they were afraid to be arrested as members of the families of the anti-Soviet element. The main routes of illegal emigration passed through the western regions of Russia to the Baltic countries, to Poland and Germany; through Central Asia to China, through Transcaucasia to Turkey and Iran, through the Far East to China and further to the countries of North and South America, to Germany. The Far East was the most successful channel of illegal mass emigration in the region of Blagoveshchensk, where refugees were supported by local Mennonite communities, the Harbin Refugee Assistance Committee, Protestant missionaries, the German consulate in China, and co-religionists in the United States and Canada. Mutual assistance at the interpersonal level, as well as between relatives and communities in different regions, continued to play the role of an effective support mechanism, maintaining ties within the Mennonite community.