Entrepreneurship is an initiator of a society and a key to a state economy. The meaning of entrepreneurship is gain and profit, while the characteristics are initiative and risk taking. Through history, the meaning of entreprenership changed, the term traditional entrepreneurship is connected to small and middle sized businesses. Small and middle sized businesses had a great impact in the development of national economies, new employment, innovation and competition, and they are also important for the industry. In the Republic of Croatia, small and middle sized entrepreneurship is regulated with the Accounting Law and the Law on promoting the development of small economy, where small and middle businesses are classified as micro, small, middle and large, based on the criteria: the amount of total active, the revenue amount, and the average number of workers during the business year. In the purpose of making this thesis the collected books define the terms of entrepreneurship, small and middle businesses, and ways of funding those small and middle businesses. The importance of entrepreneurship through history is described and the theories of small and middle businesses are presented, along with their classification. The main issue of this thesis is based on the sources of funding those businesses, the types of funding and financial institutions which are aimed at encouraging small and middle businesses and their funding. One of the main problems the entrepreneurs are facing while starting their own business or developing the existing one, is the access to the sources of funding. In this thesis there are the descriptions of some financial institutions that are enabling the access to the sources of funding by their various support programs and loans to the small and middle sized business entrepreneurs. By doing that, they are supporting their development.