The 2013 curriculum implies the use of authentic assessment that emphasizes on the assessment of students' readiness aspects, processes and students' learning outcomes as a whole. The integration of the assessment of the three components will demonstrate the students' capacity, style, and learning achievement. It is important for mathematics teachers to have the ability to conduct assessments of learning and to utilize the results of those assessments for the purposes of mathematics learning. This study aims to: (1) analyze the profile of the ability of the mathematics teachers in carrying out the authentic assessment, (2) find out the profile of the mathematics teachers' ability to apply authentic assessment results, and (3) know the constraints of the mathematics teachers in developing the authentic assessment. This research uses a quantitative descriptive method involving junior high school teachers in Yogyakarta Indonesia. Data were collected using questionnaires and triangulated with documentation and Focus Group Discussion (FGD). The results show that the ability of the junior high school teachers in Yogyakarta in applying and using the results of authentic assessment was relatively good. The teachers used authentic assessment information to design remedial and enrichment programs. This study also reveals that the teachers still experienced difficulties in developing authentic assessment instruments.