The collapse of the USSR, transition to market economy and structural changes in society had given start to the family and marriage transformation in Russia and post-soviet countries of Eastern Europe. Estonia is one of the examples of rapid deinstitutionalization of marriage, widespread of cohabitations and nonmarital births. At the same time, since first post-war decades Estonia accepted the Russian migrants throughout a long time. Research shows that adaptation of the Russian population in Estonia has proceeded slowly, and patterns of matrimonial behavior of the Russian migrants and their descendants in Estonia tend to be closer to base patterns of ethnical Russians observed in Russia. In this article the UN ECE ‘Generations and Gender’ Survey data were used to estimate and compare fertility behavior among the Russian and Estonian population in Estonia and Russians in Russia. Our results show the significant changes in reproductive behavior among Estonians and Russians in Estonia, but the probabilities of first births among Russians in Russia are stable across generations. The probabilities of second births were increasing from one generation to other among Estonians women, but contrary, decreased among Russians both in Estonia and Russia. The contribution of births in high-order unions to total number of births significantly increased both among Estonians and Russian population in Russia, as well as among Russian migrants in Estonia. At the same time, the reproductive behavior of Russians in Estonia has common features with behavior of the Russian population in Russia: the share of births in the unregistered unions is less, and length of the time interval between the first and second births in the continuous union is bigger, than for Estonians. However, there are signs of some changes in reproductive behavior among Russians in Estonia born after 1970.