Background: Critical thinking as an essential component of nursing practice represents the nurse's cognitive abilities in information processing and decision making as key components of nursing education.

Aim: To determine the effect of educational portfolio on critical thinking of nursing students.

Methods: This quasi-experimental study was conducted using pre-test, intervention and post-test. 31 seventh semester nursing students were randomly divided into case (n=15) and control (n=16) groups. In the case group, the portfolio training program was conducted under the supervision of the researcher and the control group participated in their routine program. Data collection tool was California Personal Information Questionnaire and California Critical Thinking Skills Questionnaire. Results were analyzed using descriptive statistics.

Results: The mean score of the students in the experimental group increased significantly from 5.93 to 13.87 (p = <0.001), while in the control group it increased from 0.009 to 08.9 (p = 0.095) which was not significant.

Conclusion: The results of this study indicated that portfolio method promoted critical thinking scores in nursing students.In nursing education system, critical thinking needs to be fostered by creating a proper structure and framework to present effective clinical practice. In this way, the graduates of this field can use the knowledge, thinking skills and deduction reasoning to provide reasonable services to healthy and sick people in society and health centers.

Keywords: Educational portfolio, nursing practice, nursing education