Öz
While the Covid-19 pandemic’s impact on the stock markets was a major collapse and a rapid recovery process in the first quarter of 2020, it caused a great interest in the financial markets and an increase in the number of investors. The rise in the financial markets, especially after the discovery of the vaccine, brought along a large number of public offerings. The aim of this study is to investigate the effect of initial public offerings on the volatility of the BIST 100 Index (BIST100) before and during the Covid-19 period. The study included 36 initial public offerings before the Covid-19 period (2018-2019) and during the Covid-19 period (2020-2021). In the study, the dates between 01/01/2018-31/12/2019 were selected before the Covid-19 period, and the dates 01/01/2020-28/09/2021 were examined for the Covid-19 period. As a result of the study in which GARCH models were applied, there was no significant result when the first public offerings were examined only on the first day of the IPO, to the BIST100 volatility before the Covid-19 period; It has been concluded that it reduces volatility in the Covid-19 period. The findings show that while it caused a decrease in volatility in the first 10 days of the IPO before the pandemic period, it increased the volatility during the pandemic period.