Background & Aim: Collaboration and teamwork are essential elements of nursing. Increased collaboration among nurses is critical for maintaining an effective and safe therapeutic environment. Therefore, checking the status of nurse-nurse collaboration is very important. The purpose of this study was to determine the status of nurse-nurse professional collaboration from nurses’ viewpoint in critical care units of Ardabil educational hospitals in 2017. Methods: This was a cross-sectional descriptive study. The statistical population consisted of all nurses working in intensive care units of Ardabil educational centers (216 persons). Of them, 171 nurses were selected by total sampling method, considering exlusion and inclusion criteria. Data collection tools included a demographic form and a 35-item nurse-nurse collaboration scale. Data were analyzed using descriptive (frequency, mean and standard deviation) and inferential statistics (independent t-test, one-way ANOVA, and Pearson test ) using SPSS 20 software. Results: Mean of nurses’ collaboration was 95. 36± 6. 93. Among the cooperation sub-scales, the highest levels were related to the three dimensions of professionalism (3. 12), coordination (2. 89) and collaborative processes (2. 69) and the lowest to the dimensions of conflict management (2. 51) and interaction (2. 50). There were significant and positive relationships between nursing work experience (r=0. 194, p=0. 011), work experience in intensive care units (r=0. 165, p=0. 031), age (r=0. 284, p<0. 001), hospital workplace (F=2. 83, p=0. 026), workplace unit (F=5. 044, p<0. 001) and work shift (t=2. 25, p=0. 024) with nurses’ professional collaboration. Conclusions: Due to the low scores of conflict management and interaction dimensions among nurses, holding workshops on how to improve communication, training the conflict resolution skills, teamwork practice in student time, organizational support and quality improvement of nursing work environments can be effective steps in increasing nurse-nurse collaboration.