The relevance of this issue is connected with the strengthening of expert and public criticism of Russia's migration policy. Currently, there is a sharp polarization of opinions of the scientific community about the role of external migration on the demographic development of the country, including the processes of marriage and fertility. The scientific problem consisted in the development of research approaches that allow solving theoretical and applied problems of assessing the impact of external migration on the processes of marriage and fertility in modern Russia. Traditional methods of scientific research were used in the work: analysis, synthesis, grouping, comparison, generalization, structural and graphic. The theoretical aspects of this study allowed us, on the basis of the sign of civil status, to form a logical structure of categories of the population exercising marital and reproductive behavior in modern Russia, as well as to introduce the following definitions into the scientific information space: determinate by civil status population and nondetermined by civil status population, as well as Russian marriage and fertility, foreign marriage and fertility, marriage and fertility with a foreign component. The applied results of the work made it possible to obtain a scientifically based assessment of the contribution to the trends of marriage and fertility of certain categories of the population differentiated by nationality, which, in turn, made it possible to obtain a scientifically based idea of the extent of the influence of external migrant flows on the marital and reproductive sphere. The foreign factor, as a result of external migration, tends to increase in the formation of marriage and fertility trends, although its importance is small in modern Russia.