This study aims to determine the effect of the contextual approach to students' mathematical reasoning abilities in one junior high school in the city of Bandung. The method of this research is qualitative descriptive. The subjects in this study were class VIII students in one junior high school in Bandung as many as 32 students. This study uses Classroom Action Research (PTK) with data collection techniques carried out, namely test instruments mathematical reasoning abilities as many as 5 items. The results of learning research using a contextual approach by performing pretest and posttest tests can affect the mathematical reasoning abilities of junior high school students with an average percentage of 81%