As we know, individuals go through some mental processes such as reasoning, analysing and evaluating the situation during the both educational life and daily living. The critical thinking; which contains these mental processes, is also identified as a thinking style which aims to obtain the information originally, compare and use. The critical thinking ability is also related with high level mental processes; such as problem solving, problem posing and reasoning and it is also highly important for mathematical education. The aim of this study is to determine the level of critical thinking tendency of prospective mathematics teachers and examine this tendency by different variables. For this purpose; California Critical Thinking Tendency Scale which is developed by Facione et al. in 1998, is applied to prospective mathematics teachers in a public university in Ankara City. Besides this scale; a form is given to prospective mathematics teachers which checks up the demographic information. In the direction of obtained data; the critical thinking tendency of prospective mathematics teachers is both examined by variables such as gender, grade level, graduated high school and teaching experience and the analysis of data is also made according to each sub-dimension included in the scale. According to the results evaluation and recommendation are made about critical thinking tendency of prospective mathematics teachers.