Aims: One of the most important nursing interventions for the patients using endotracheal tube is on time and accurate discharge of respiratory tract secretions. Improving nurses’ performance in taking care of the newborns with endotracheal tube is an important factor in reducing side effects of frequent suctioning and acceleration in patients’ improvement. This study has been done in order to “assess nurses' performance in endotracheal tube suctioning in Neonatal Intensive Care Units (NICU)”.Methods: It is a descriptive-cross sectional study. 48 nurses working in NICU of the training hospitals affiliated to Ahvaz Medical Sciences University were chosen through census method in 2014. A questionnaire was prepared to assess nurses' performance before, during and after endotracheal tube suctioning and to compare their performance according to suctioning standard procedure; the questionnaire was consisted of demographic information and a standard checklist regarding endotracheal tube suctioning. Data analysis was done through using descriptive statistical test and SPSS 19 software.Results: 83.4 percent of the workers were women and 16.6 percent were men and they were 26-35 years old. 54.1 percent had attended intensive care in service-training. 52.1 percent of the nurses had 5 years or less working experiences in ICUs. 64.6 percent had good performance and 35.4 percent had medium to poor performance.Conclusions: According to the results of the present study, most of the nurses working in ICUs had good performance regarding endotracheal tube suctioning. So it is necessary to consider in-service training regarding correct and appropriate endotracheal tube suctioning for those who did not have good performance too, since lack of appropriate performance of endotracheal tube suctioning by a small number of nurses might be dangerous for the patients hospitalized in ICUs.