Background: Coronavirus disease of 2019 (COVID-19) is a global pandemic. It affected thousands of people and a lot of them were serious cases and admitted to isolated intensive care units (ICUs), so COVID-19 was a horrific incident. Critical care nurses (CCNs) were front liners in managing these situations which led them to be exposed to many negative health outcomes. Post-traumatic stress disorder (PTSD) is among the serious mental problems that has arisen as a pandemic consequence. If not identified and treated promptly, elevated levels of it can negatively affect productivity and life quality. Aim: This study aimed to assess post-traumatic stress disorder among CCNs caring for COVID-19 patients. Method: A descriptive cross-sectional design with a convenience sample of 109 CCNs work in 13 isolated ICUs from three hospitals in Egypt which are designated to take care of Corona patients. Data was collected through post-traumatic stress disorder assessment questionnaire sheet. Results: In total, 23.9% of participant nurses had provisional PTSD diagnosis. Also, all four domains had high scores in participant nurses with provisional PTSD (P < 0.05). Shortage of protective equipment, overtime in ICU and the number of exposures to COVID-19 are significant factors for PTSD occurrence. Conclusion: Nearly one-quarter of CCNs had a provisional PTSD diagnosis. The symptoms included negative alterations in cognition or mood and hyperarousal domains are mostly affected in CCNs diagnosed with provisional PTSD. Recommendations: A health education program could be utilized to help nurses deal with PTSD and offer mental assistance during epidemics, such as COVID-19.