The Croatian National Bank “CNB” is an essential institution in the Croatian financial system, aiming to provide economic stability and growth. It is part of the Eurosystem, and it takes part in the formulation and execution of the European Union's monetary policy. The CNB's historical background is an important starting point for comprehending its current importance. We may acquire a better grasp of how the organization adjusted to Croatia's evolving economic landscape by delving into its origins and significant milestones. Following the history, this thesis examines the functions of the CNB. It is responsible for a wide variety of functions, including monetary policy implementation and formulation, supervising, and regulating other financial institutions in Croatia, ensuring a stable financial infrastructure, and fulfilling its primary purpose – price stability. The significance of monetary policy is then discussed, along with its theoretical foundations, numerous tools, and the CNB's role in implementing it. The success of a country's monetary policy may have a substantial impact on both its citizens and the country's economic prosperity, and this is why it is a significant task of the CNB. An important focus of this thesis will be dedicated to the overview of the CNB’s operations on the open market as well as how the CNB used them in response to the COVID-19 crisis. In addition, the thesis will examine how the CNB uses interest rates to influence borrowing costs, investment decisions, and the broader financial environment of Croatia. Through an in-depth examination of its history, functions, monetary policy execution, open market operations, and effect on interest rates, the aim of this thesis is to shed light on the Croatian National Bank's critical role in the Croatian financial environment. By understanding more about the Croatian National Bank, we may have a better understanding of the dynamics of the Croatian economy and the mechanisms utilized to maintain its stability and growth.