Self-esteem is one of the factors from within students that affect learning outcomes and achievement. Learning outcomes can be obtained from students’ report book which shows the average of the accumulation of all student scores for one semester and also reflect all students’ achievements in the process of participating in learning. Therefore, this research aims to determine the effect of self-esteem on mathematics learning outcomes of students at SMK Muhammadiyah 1 Temon, Kulon Progo, Yogyakarta. The population in this study were grade XI students of SMK Muhammadiyah 1 Temon. The sampling method used in this research is purposive sampling and obtained 32 students of class XI SMK Muhammadiyah 1 Temon as the subjects. The data collection was conducted using the method of distributing questionnaires and collecting student learning outcomes in the form of transcripts of students' report book in mathematics subject for the 2020/2021 Akademic Year. The questionnaire instrument was adopted from the research of Naike (2017), and then analyzed using descriptive statistical analysis techniques and simple linear regression analysis using SPSS version 25 application. The results showed a relationship between self-esteem and learning outcomes with a significance value of 0.022. In addition, the coefficient of determination (R Square) is 0.162. This shows that self-esteem affects the learning outcomes of SMK students by 16.2%.