Introduction: Critical thinking is an essential part of clinical decision making and professional competence of nurses. One of the proposed ways to create such traits in students is their education with an active and problem-oriented method such as problem based learning. This study was conducted to determine the effect of problem based learning training on critical thinking skills of fourth-year nursing students studying at Faculty of Midwifery at Urmia University of Medical Sciences (UUMS).

Method: This is a quasi-experimental study undertook in semester 1 -2013 with 50 year four nursing students participated from Faculty of Midwifery of UUMS. Seventh semester nursing students was recruited to the intervention arm and eighth semester nursing students to the control arm. Data collection tool was a standard California Critical Thinking Skills Questionnaire. All participants completed the questionnaires before and after problem based learning training workshops. Students in the intervention arm attended in the three small groups of problem solving education classes for six sessions.

Results: Critical thinking skills in the intervention arm was significantly better than the control arm after problem based learning training (P<0.001). Comparing the two arms, the mean difference in critical thinking scores in both arms was significantly difference between the two arms after intervention (P<0.001).

Conclusion: Problem based learning training promotes critical thinking skills over the traditional learning in nursing students. Therefore, this method is suggested to be used in training nursing students.