This study aims to describe the readiness of prospective mathematics teachers in implementing the STEM (Science, Technology, Engineering, and Mathematics) approach in mathematics learning. The method used is qualitative descriptive, involving 8 students from 4 universities—2 in Ponorogo and 2 in Yogyakarta—as research subjects. The data collection instruments consist of questionnaires and interviews designed based on four main aspects: conceptual knowledge of STEM, perceptions of STEM learning, self-efficacy in integrating STEM, and pedagogical knowledge of STEM. The questionnaire results indicated that the students' readiness was in the high category, with an overall average score of 84.23%. In-depth interviews revealed that the students had a good understanding of STEM concepts and demonstrated positive attitudes toward their application, but still required reinforcement in practice and assessment. These findings suggest the need for practice-based training and hands-on experience to enhance prospective teachers' readiness in effectively implementing STEM-based learning in mathematics classrooms.