Pension funds are one of the main contributions to an efficient financial system used to promote long term savings and encourage economic and financial development. In recent decades, the strong development of pens ion funds has been contributed to by the growing demand stemming from an aging population. Pension funds are of significant political and social importance and their establishment, operation and investment are of particular interest in each country. They invest large amounts of money in long term capital market instruments and are the most significant buyers of government bonds. Each investor is the owner of his account in the pension fund and can see the amount of available funds at any time, in the amount of the expected amount paid after retirement. They are divided into mandatory and voluntary pension funds. Over the last two decades, mandatory pension funds have become the fastest growing financial institutions that have completely changed the financial system. There are four mandatory pension funds in Croatia, namely: AZ, Erste Plavi, PBZ Croatia Osiguranje and Raiffeisen OMF. Every employed citizen of the Republic of Croatia is a member of one of these pension funds and has the opportunity to choose be tween three categories of sub funds: A, B and C. After the theoretical part, the analysis of the yield of all four mandatory pension funds in the Republic of Croatia from its establishment to the period of the COVID 19 pandemic and during its time, given that it left a mark on savings in voluntary and mandatory pension funds.