Abstract: The aim of our work was to assess the cognitive function in patients recovered from COVID-19 infection using P300 analysis. 50 subjects recovered from COVID-19 infection (at least 8 weeks following recovery). The patients were recruited in the period between April 2022 and December 2022.The cases were recruited from the Chest hospital, Beni-Suef governorate and from chest department, Beni-Suef University hospital. Our results revealed significantly impaired cognitive function, delayed P300 latency and small P300 amplitude among severe cases. Also, there was a significantly delayed P300 latency and small amplitude in hypoxic critically severe patients. In addition, our results revealed a significant positive correlation between cognitive function, P300 latency, and the duration of hospital stay. Also our study detect the value of vaccination we revealed that patients who received vaccination before COVID-19 infection had less delay in P300 latency in comparison to those who did not receive vaccination before infection.