21st-century skills can be applied to STEM education. The Merdeka Curriculum also has a passion to support teachers and schools in exploring and implementing STEM as a learning approach to improve student competence. The study aims to develop learning tools consisting of the syllabus, lesson plans, and student worksheets (SLS) that are valid and practical. This study uses the ADDIE development model. The research involved 43 participants at SMAN 6 Malang. Learning tools are validated by material experts, learning experts, and field practitioners. The research was conducted only as a trial or formative evaluation in the development stage. Formative evaluation includes three stages of testing, namely individual tests of 3 students, small group tests of 10 students, and field tests of 30 students that have passed the material of bacteria. The results of practicality obtained through questionnaires on student responses to worksheets on individual tests, small groups, and field tests showed percentages of 89.85%, 88.14%, and 89.08%. These results indicate that STEM-PBL model on bacterial material is very valid and practiced using and can train critical thinking skills, creativity, and cognitive learning outcomes of 10th-grade students. [For the complete proceedings, see ED655360.]