During infectious disease outbreaks, the knowledge and attitudes level of individuals involved in patient care is controversial. This cross-sectional study assessed the levels of knowledge and attitudes of Iranian nursing students regarding COVID-19 to determine their educational needs and take the necessary measures for their readiness. A total of 302 nursing students completed a valid and reliable researcher-made questionnaire through a web-based survey to collect data. 54% were women among the participants, and 51.32% were over 20. The mean (SD = standard deviation) scores of knowledge and attitudes were 17.99 (SD = 5.26) and 3.68 (SD = 1.15), respectively. According to the classification of total knowledge score, the unsatisfactory, satisfactory, and excellent levels were 55.30%, 18.50%, and 26.20%, respectively. The knowledge levels of nursing care for COVID-19 patients, sampling method for diagnostic purposes, medications used during COVID-19 treatment, and the clinical course of COVID-19 were thus lower than other issues. The mean score of attitudes was also 3.68 (SD = 1.15), representing the nursing students' positive attitudes towards caring for COVID-19 patients. The results of the Spearman correlation coefficient between knowledge and attitude about COVID-19 showed a significant positive relationship between the total knowledge and attitude scores (r = 0.23, p < 0.001). Therefore, given the knowledge levels, particularly the unsatisfactory level in nursing care for COVID-19 patients, and the relatively positive attitudes towards this condition, it is helpful to implement training programs to improve the nursing students' knowledge and clinical skills.