The paper addresses sustainability concept implementation in the context of investment decisions maked on modern financial markets. The starting point of the research is theoretical analysis of sustainable investment as a scientific category. It creates required methodological prerequisites for the characteristics of the world market for sustainable investment. The research is based on a systems approach. In the framework of this approach, general scientific and special financial research methods are applied including methods of systematization, classification, and descriptive statistics. Major research results contains: a) revealing the content of the sustainable investment concept in relationship with categories of socially responsible investment (SRI), responsible investment (RI) and social or socially directed investment (SI or SDI); b) providing a systematic view on the market segment of the sustainable investment system; c) considering the global profile of sustainable investment decisions on financial markets.