Purpose To assess Turkish oncology nurses' knowledge regarding novel coronavirus (COVID-19) during the current outbreak in Turkey. Methods This descriptive study was carried out with the 185 oncology nurses between April and May 2020 in Turkey. Research data were collected through online survey using "Nurse Information Form" and "Nurse Information Scale for COVID-19." Multilinear regression analysis was used in determining the factors affecting oncology nurses' information regarding COVID-19. Results According to the data delivered from 185 oncology nurses, 57.7% of the participants had an undergraduate degree, 74.1% were working in adult oncology units, and 52.4% of them were working as clinical nurses, 48.1% of the nurses received education for COVID-19 (51.9% did not receive) and 70.3% followed and read the COVID-19 Guidelines published by the Ministry of Health (29.7% did not follow guidelines). Using multiple regression analysis, a model based on the relationship between the variables was created. In the model, the descriptive characteristics of the oncology nurses and their experiences of COVID-19 were found to explain 29.1% of their knowledge level for COVID-19. Nurses' education level, the presence of a relative diagnosed with COVID-19, and following the COVID-19 guidelines were found to statistically significantly affect the knowledge levels of COVID-19. Conclusion These findings suggest that hospital management and the Ministry of Health should provide more information for the oncology nurses to better control of cancer patients from the infectious disease.