Purpose- Financial performance indicators of the pandemic effect in companies operating in BIST-30 were grouped as pre-pandemic and pandemic period, and it was tried to determine whether there were clustering differences between companies by using the cluster analysis method. Methodology- Within the scope of the study, financial performance indicators of current ratio, liquidity ratio, leverage ratio, return on equity, return on assets, net profit margin, equity/assets and current assets/assets of the companies operating in BIST-30 for the years 2018, 2019, 2020 and 2021 were used. The data for 2018 and 2019 are grouped as pre-pandemic, while the data for 2020 and 2021 are grouped as the pandemic period. These indicators were obtained from Stockeys and KAP. Cluster analysis was applied to the data. Ward technique was used in cluster analysis. SPSS Statistics 22 program was used in the study. Findings- In the cluster analysis conducted in the context of financial performance indicators, 3 clusters were identified before and during the pandemic. While companies operating in the mining sector were in one of the clusters before the pandemic, it was determined that the other clusters did not form a sectoral unity within themselves. While companies operating in the mining sector were located in one of the clusters formed during the pandemic period, companies operating in the transportation sector were clustered in the other cluster. It has been determined that the companies in the other cluster do not form a union on a sectoral basis. Conclusion- As a result of the analysis, it was determined that companies operating in the mining sector were separated from other clusters before and during the pandemic. It has been determined that companies operating in the transportation sector have differentiated from other companies during the pandemic period and formed a new cluster. Except for the mining and transportation sectors, no difference was detected between the clusters before the pandemic and during the pandemic period. One of the reasons why the enterprises operating in the mining sector are in a separate cluster during the pandemic period can be considered as the increase in commodity prices during the pandemic period. The reason why companies operating in the transportation sector are in different clusters can be considered as the negative reflection of the closure of flights in the pandemic period on the balance sheet of the companies. Keywords: Covid-19, financial performance, cluster analysis JEL Codes: I19, G14 ,C38