Background: Requiring for critical thinking in nursing accentuated in response to speed changing health care atmospheres. Nursing students should bethink to give effective care whilst coping with expansion f role for associated by complexities of current health care. Present study aimed to assessment of critical thinking training program effects on developing reflective thinking. Methods: Quasi-experimental design used in ourinvestigation. A stratified proportionate random sample of 317 students was chosen from faculty of Nursing, Zagazig University that enrolled in the academic year 2017-2018. Data were collected using four tools namely; nursing students' knowledge assessment questionnaire, California critical thinking skills test, reflective thinking questionnaire. Results: All nursing students (100%) had inadequate knowledge pre implementation program. While, after the program implementation all of them (100%) had adequate knowledge. Additionally, 74.4% of nurses have deficiency of critical thinking pre the program implementation. In contrast, all of them have strong levelspost program implementation (100%). Likewise, 62.5% of nursing students had high level of reflective thinking before the program implementation that had increased to 100% after the program implementation. Conclusion: there's no statistically significant relation between critical thinking, reflective thinking before the program implementation while there is statistically significant correlation between critical thinking, reflective thinking after the program implementation. Therefore, it is recommended that nurse educators should develop continuous in service- training and education program for refreshing and increasing nursing students' knowledge and skills about concept of critical thinking as well as to emphasize reflective thinking.