Introduction: Mentorship is a voluntary and beneficial professional relationship in which a person with more experience and knowledge (Mentor) support a person with less experience (mentee). This study aimed to investigate the effect of the mentorship on the level of stress in the nursing students. Methods: In this semi experimental study, 57 seventh and eighth semester nursing students of Shahrood Nursing and Midwifery School were selected through census. They were divided into two groups of control (28) and intervention (29) using the simple random method. In the experimental group, there was a nursing expert as the mentor for each 6-7 students. Stress of students was evaluated using a clinical environmental stress questionnaire before and after the training. Data were analyzed using SPSS version 18 and independent t-test, chi-square and covariance. Results: There was no significant difference between the two groups in terms of age and educational level. Based on covariance analysis, before the intervention, the two groups had a significant difference in the mean score of stress (P = 0.418). However, stress scores significantly decreased in the intervention group after the intervention (P = 0.016). Conclusions: Mentorship training program can reduce stress of nursing students and is recommended to be used in field training instead of the usual methods in nursing faculties. This program can be used due to the shortage of nursing educators and in order to reduce the gap between theory and practice.