This study aims to analyze the mathematical critical thinking skills and processes of junior high school students on the Pythagorean Theorem material based on ethnomathematics of traditional Tongkonan houses in Tana Toraja. This study uses a descriptive qualitative approach with 28 eighth-grade students of Dende' Christian Junior High School as research subjects. The research instrument is a descriptive essay test based on Higher Order Thinking Skills (HOTS) contextualized with local culture and supporting interviews to explore students' thinking processes. The analysis of mathematical critical thinking skills is based on four indicators, namely interpretation, analysis, evaluation, and inference. The results show that students' mathematical critical thinking skills are generally in the sufficient to good category. The analysis and inference indicators show higher achievements, indicating that students are able to identify important information, model problems mathematically, and draw conclusions based on the Pythagorean Theorem concept. However, the evaluation and explanation indicators are still in the low category, especially in assessing the logic of results and conveying mathematical arguments systematically. Ethnomathematics-based learning in the Tongkonan traditional house helps students understand mathematical concepts more concretely and meaningfully because it is linked to a cultural context close to their lives. Therefore, ethnomathematics can be used as an alternative learning approach to support the development of critical mathematical thinking skills in junior high school students.