Background: Many patients with severe traumatic injuries are admitted to intensive care units (ICU). These patients usually require prolonged mechanical ventilation. These interventions require oral intubation and leave the mouth open which consequently impairs the natural antimicrobial activity in the mouth and airways. These patients are also prone to ventilator-associated pneumonia (VAP). Evidence shows that paying attention to oral hygiene in patients under mechanical ventilation is important in helping to prevent VAP. Objectives: The present study was conducted to assess the viewpoints and performance of ICU nurses at Birjand hospitals towards oral care of patients under mechanical ventilation. Patients and Methods: A cross-sectional study was conducted at ICUs of Imam-Reza and Vali-Asr hospitals, Birjand, Iran. Sampling was done through a census in which 53 ICU nurses participated. Descriptive statistics, Kolmogorov-Smirnov test, Mann-Whitney U tests and Kendall's correlation coefficient were used to analyze the data. Results: A total of 53 nurses participated in this study. Most of the nurses had been trained to provide oral care during their university education. According to the participants' opinions, oral care with an average score of 5.72 ranked second among the 10 nursing care domains. The most frequent oral care provided was oral suctioning, normal saline irrigation, and chlorhexidine rinse with 95%, 90%, and 81.3% frequency, respectively. Conclusions: Nurses participating in this study considered oral care to be of prime importance. Most of the participants although trained in this area felt the need for continuing training courses.