The research is devoted to institutions of the market for sustainable financial services and is aimed at substantiating and testing a methodological approach to the systematization of these institutions. The author's approach integrates the results of summarizing and identifying the comparative importance of innovative financial solutions in the system of traditional ideas about the content and structure of the financial corporations sector and the financial services they provide. In particular, a classification matrix is proposed that includes the main types of financial institutions, sustainable financial services provided by these institutions, the role of relevant institutions in the development of the market for sustainable financial services, and professional initiatives undertaken by them in this area. When developing the matrix, hierarchical and facet classification methods were used. It is shown that, based on the proposed matrix, a systematic characterization of the institutions of the market for sustainable financial services can be given (examples are central banks, depository corporations, and stock exchanges). Besides, this matrix can be used as the basis for further deeper research in the field of sustainable financial development. Thus, the results contribute to the topical discussion on the taxonomy of sustainable finance, refining and developing earlier studies.