This research aimed to describe decision making skill in solving mathematical problem on students of SMK Bina Teknologi Purwokerto. This was a descriptive qualitative research with the subjects of eleventh-grade students of TKJ (Computer and Network Engineering) taken using purposive sampling technique. The students were divided into four categories based on the ways of thinking including concrete sequential, abstract sequential, concrete random, and abstract random. The data were collected using questionnaires, tests, interviews, and documentation and the validation test was technique triangulation. Based on the results, it could be concluded that students with a concrete sequential way of thinking were able to identify the problem in a question, determine the alternative answer, count, and do the questions given and are able to determine the results of decisions according to the objectives of the questions. The students with an abstract sequential way of thinking were able to identify the problem in a question, determine the alternative answer but tended to be less careful in counting and doing the questions. Students with concrete random and abstract random way of thinking were able to identify the problem in a question and tended to use personal thought in counting and doing the questions.