Investment institutions are present all over the world, and they are important because they provide services to their clients. The use of their services enables clients to invest in various forms of financial assets, in which institutions play the role of intermediaries. Financial intermediaries are of particular importance to small investors who do not have direct access to the financial market. A person who has excess financial resources can decide to invest and, according to this decision, choose through which financial intermediary he wants to obtain a return on the invested amount. Depending on the risk appetite, the investor decides whether to invest in mutual funds or channel financial resources to brokers or dealers. Before investing, the investor should familiarize himself with the different categories of funds or companies, as different financial intermediaries are associated with different business conditions. Investment in mutual funds is considered to be a safer form of investment, as the assets are distributed among several investors, thus reducing the risk. This paper analyzes the investment funds and the evolution of the number of UCITS funds and AIF funds, as well as the evolution of their net assets. The mentioned types of funds were observed in the Republic of Croatia and in the Republic of Slovenia in the period from 2015 to 2021. The analysis shows that the total number and total net assets of UCITS and AIF funds increase in the observed period in the Republic of Croatia. Also in the Republic of Slovenia, there was a decrease in the total number of UCITS funds and an increase in their net assets, as well as an increase in the total number of AIF funds and an increase in their assets.