PBL is anchored by Students Centered Learning (SCL) concepts that follow constructivist learning theory principles. The study specifically evaluated the effect of problem-based learning on the mathematical skills of students. The research subjects were 143 grade eleven senior high school students taking academic strand. The research design used in this study are quasi-experimental research design for determining the mathematical skills of the students before and after the exposure to Problem-based Learning and descriptive research design in describing the level of the Problem-based Learning using the criteria from a questionnaire. The research instrument was a validated questionnaire about the Problem-based Learning also the test about Mathematical Skills, and the data were analyzed by using two ways t-test and Pearson R. The research found that the test of difference between before and after the exposure to Problem-based Learning of the respondents resulted that there is a significant difference in the level of the mathematical skills. Furthermore, this research also found that there is no significant effect of problem-based learning approach to the students mathematical skills.