The aim of the research is to analyze the effectiveness level of the development of the Realistic mathematics education based on Toba Batak culture learning model. The Realistic mathematics education based on Toba Batak culture learning model has fulfilled the effectiveness level to enhance students' HOTS abilities, which include: (a) syntax, consisting of: cultural apperception, problem-solving discussions, patterns of social interaction using representation and problem-solving, reflection on work results, (b) social system built on collaboration principles, (c) management reaction principles where lecturers act as facilitators, (d) supporting system such as: semester lecture plans, teaching materials, lecturer guidebooks, student guidebooks, and student activity sheets, (e) instructional impact in the form of students' HOTS abilities and accompanying impact in the form of scientific attitudes, collaboration, and realistic thinking. The Realistic mathematics education based on Toba Batak culture learning model is equipped with a set of model books, semester lecture plans, teaching materials, lecturer guidebooks, student handbooks, and student activity sheets that have met the effectiveness level. The effectiveness level of the Realistic mathematics education based on Toba Batak culture learning model is influenced by four aspects, namely: The lecturer's capacity to oversee learning scored 4.17 on the NKD scale, placing it in the high category. Student's Higher Order Thinking Skills (HOTS) were rated at 0.85, indicating a high level of proficiency. Active student participation was noted at 25%, categorized as active. Student responses were at 93%, indicating a high level of engagement. The level of students' HOTS abilities through the application of the Realistic mathematics education based on Toba Batak culture learning model has increased from the moderate category to the high category, with an N-Gain score of 0.81 in the high category. The level of active student activities through the application of the Realistic mathematics education based on Toba Batak culture learning model has a value of 25% in the active category. The level of student response to the learning process in implementing the Realistic mathematics education based on Toba Batak culture learning model obtains a value of 93 in the high category.