This study was conducted to develop and evaluate the effectiveness of the Fermi problem approach in enhancing measurement estimation skills in mathematics. Employing an action research design, 24 seventh-grade students (13 girls and 11 boys) from a southern Turkish middle school were selected using criterion sampling. Quantitative data were gathered through a Measurement Estimation Skill Readiness Test and tasks based on the Fermi problem approach, complemented by qualitative insights from student reflective diaries. The 10-week action research study consisted of three cycles, each focusing on different aspects of measurement estimation: length, area, and volume in the first cycle; liquid measurement and volume in the second cycle; and weight estimation with Fermi problems in the third cycle. The findings highlighted the effectiveness of the Fermi problem approach in enhancing the measurement estimation skills of seventh-grade students. The research findings suggest that incorporating Fermi problems into the problem-solving process in instructional programs may offer significant contributions in providing a different perspective on the development of students' measurement estimation skills.