This study aims to: (1) describe the level of difficulty of the teacher in planning, implementing and evaluating mechanical engineering learning; and (2) knowing what dimensions are most difficult for teachers in mechanical engineering learning. This research is a descriptive study with a quantitative approach. The population of this study were all mechanical engineering SMK teachers in the city of Medan, amounting to 36 people. Data collection techniques used are questionnaires. The data analysis technique used is statistical-descriptive analysis. Based on the results of the study showed that: (1) The level of difficulty of the teacher in the main task and function of the teacher generally included in the category of not difficult that is equal to 80.55%. However, there are still some teachers in the very difficult category, which is 5.56%. (2) the teacher in carrying out the stages of planning, implementing and assessing authentic learning falls into the category of not difficult. (3) the dimension that is most difficult for teachers in learning is the authentic assessment dimension; and (4) male teachers and non-government employees have more difficulty in carrying out authentic planning and assessment stages in the 2013 Curriculum.