This study was conducted to determine the effectiveness of the flipped classroom model in teaching functions to STEM learners at Garcia College of Technology – Senior High School Department. It employed a true experimental research design, using a pre-test–post-test control group approach and a random sampling method. Two instructional methods were utilized: traditional instruction and the flipped classroom model. The results of the pre-tests and post-tests were compared, using the same set of examination questions administered to both groups. The participants were 40 selected Grade 11 students, matched and paired according to their average Grade 10 performance and sex. The study was conducted from July 2024 to December 2024. The average pre-test score of learners in the traditional classroom was classified as “Proficient,” while those in the flipped classroom were classified as “Highly Proficient.” Similarly, in the post-test, the average score of STEM learners in the traditional classroom remained at the “Proficient” level, while those in the flipped classroom continued to perform at the “Highly Proficient” level. Furthermore, there was a statistically significant difference between the pre-test and post-test scores within both the traditional and flipped classroom groups. However, the difference between the pre-test and post-test scores across the two groups was not statistically significant. This suggests that while STEM learners demonstrated adequate understanding of the material through traditional instruction, the flipped classroom setup contributed to overall better performance. The results indicate that both traditional and flipped classroom methods were effective in enhancing learners’ understanding of mathematical concepts, particularly in the topic of functions.