The socio-economic development of modern Russia is largely determined by migration processes. St. Petersburg is one of the largest centers of attraction for labor migrants from near and far abroad. Because of migration in conditions of turbulent development of the economic and social spheres, unequal distribution of benefits and shortage of resources, new challenges and risks arise for the host society. The presence of risks, as well as their perception and assessment by members of the society, underlies the development of social tension and can increase the level of conflict between different groups of population. The aim of the study is to identify and describe risks for the host community in the context of migration in St. Petersburg. The analysis of theoretical concepts of social risk and social tension made it possible to identify approaches being the most relevant and meeting research goals and also to supplement them in terms of international migration processes and to formulate the authors' understanding of the grounds for social tension. The article presents the authors' concept of social risks due to international migration for the host community, which is based on the study of subjective risk assessment by members of this community (public opinion of St. Petersburg residents), as well as on the analysis of objective characteristics of risks. The research methods included telephone interviewing (standardized interview), analysis of the federal and departmental statistics, and expert opinions. The study identified and described the main social migration-related risks that can increase social tension. These risks require special attention and further scientific reflection while developing the migration policy of St. Petersburg as well as in elaborating measures to reduce social tensions in society as a whole.