Epistemological obstacle is emphasized in mathematics education. Students often have limited students' context of knowledge in understanding trigonometry. Knowing the epistemology obstacle can help a teacher understand the student's misconception. Therefore, this study aimed to identify students' epistemological obstacles of trigonometry and trigonometric function. This research used two subjects of 11th grade high learners of high school. The research data were collected in audio, photograph, and trigonometry test. Data were analyzed by using in and between conditions students interview. This study suggests that students tend to associate the trigonometric value into a particular angle, such as having difficulty using angle in radian and could not recognize the value of p. They also tend to follow the procedural steps in converting angle from radian to degree and vice versa without knowing how the formula is constructed. They have difficulty figuring out the trigonometric function's value, especially for angle in the quadrant and the coordinate of a point trigonometry graph, primarily related to the radian unit.