The study aims to describe vocational high school teachers' difficulties in implementing the assessment within Curriculum 2013, which has been implemented since July 2013 in several Indonesian schools and which might have been in effect in all schools around 2014. The study was descriptive explorative research by means of qualitative data gathering. The data of vocational high school teachers' difficulties in implementing the assessment within the Curriculum 2013 were gathered by means of interviews and focus group discussions. The data source was 22 vocational high school teachers and the vice principals of curriculum in the Province of Yogyakarta Special Region of Indonesia. The data analysis was conducted by looking for the specific theme; then, the researcher found the inter-theme relationship in order to attain the proper understanding. The results of the study showed that in the assessment implementation of Curriculum 2013 the teachers had not fully understand the assessment system. The teachers' difficulties were also found in: developing the instrument of attitude, implementing the authentic assessment, formulating the indicators, designing the assessment rubric for the skills, and gathering the scores from multiple measurement techniques. In addition, the teachers could not find feasible application for describing the students' learning achievements.