The aim of this study is to examine the effects of Realistic Mathematics Education (RME) on 7th grade students' achievement on integer operations and their attitudes towards mathematics and to determine students' views about the RME approach. The research was carried out with the participation of 11 students. Exploratory sequential mixed design was used. In the quantitative part of the research, one group pre-test-post-test design as one of the weak experimental designs was used. On the other hand, case study was used in the qualitative part. In the research, the achievement test consisting of 10 open-ended questions prepared by the researcher and the mathematics attitude scale developed by the Department of Education Research and Development (EARGED) were used as quantitative data sources. On the other hand, semi-structured interview form developed by the researcher and student diaries were collected as qualitative data sources. Also, they were asked to write a diary in which they expressed their opinions about the activities in each week, and interviews were held within 3 weeks after the application had been completed. As a result of the research, it was observed that Realistic Mathematics Education increased the students' achievement and positively affected their attitudes towards mathematics.