The article substantiates the necessity and fruitfulness of using the conceptual approaches of social constructivism in the study of social capital and a culture of trust. The characteristic of A. Giddens' theory of structuration, the structural-genetic socio-analysis of P. Bourdieu and the concept of spontaneous socialization of F. Fukuyama are given. The definition of social capital as a complex socio-cultural system is clarified, key conditions and factors of its formation are analyzed, and the specifics of the becoming of a culture of social trust in modern Russia are shown.