The article addresses problems related to harmonization of the financial market legislation (the banking sphere, the securities market and the insurance field) in countries of the Common Economic Space (the Republic of Belarus, the Republic of Kazakhstan, the Russian Federation). The retrospective survey traces the evolution of integration processes in the CIS that resulted in the formation of the Customs Union and the Common Economic Space of the three countries thereby creating preconditions for establishment of a common financial market. The key trends and problems of the legislation harmonization are highlighted that are related to definition of minimum prudential requirements for the financial market players, issues of licensing their activities, protection of interests of investors, establishment of supernational regulation authorities.