Aim: This study was conducted to determine the level of critical thinking and the factors affecting critical thinking of the fırst and last grade nursing students. Method: This descriptive study, School of Health of Nursing Department was carried out at a state university. This study was carried out with first and last grade students that might have the most different levels of critical thinking in 2013-2014 academic years’ spring semester. A total of 210 students from 160 of the first and the last grade students who accepted to participate in the study. Data of research was collected by using Personal Information Form and California Critical Thinking Disposition Inventory (CCTDI). The data were analyzed using by descriptive (mean, standard deviation, percentage) and comparative statistical tests (Mann-Whitney U Test and Kruskal Wallis Test). Results: The mean score of critical thinking of nursing students is calculated 252.50±28.96, CCTDI subscale scores between the highest mean scores of students from analytical thinking subscale (46.03±7.13), while the lowest score from the right call subscale (37.36±6.90) was determined. Students in the class of continued, the school graduation of students’, mother's education, income level and family structure has been found to affect the level of critical thinking of students'. Conclusion: Moderate levels of critical thinking in nursing students during their education must be supported to develop critical thinking skills. İt is important that active learning environment be established, necessary guidance be made by supporting qualified inquiries and interrogation, and the development of critical thinking be supported.