Mathematics and proof are two closely related concepts. Mathematics not only shows what is right or wrong, but it also teaches that it is not enough to know the latest formulas and results should be explained with causality. In this context, students learn the underlying meaning behind what mathematicians do by way of proofs. Accordingly, this study aims to analyse the mathematical proof skills of students studying science teaching. The study group is composed of 50 first-year college students studying science teaching in the academic year 2011-2012. The study employs case study method as a form of qualitative research and six open-ended questions are used for data gathering purposes. The obtained data show that students successfully employ mathematical proof methods (induction, deduction etc.), but the majority of the students accepted the technique of giving a numerical value as a method of proof.