The Feynman Technique is a mental model and learning strategy used to simplify any complex information. This study endeavors to provide empirical evidence on the effectiveness of the Feynman Technique as a heutagogy-based learning strategy that fits the e-learning landscape. Utilizing true experimental research design, grades 4, 7, and 11 students from typical elementary and national high schools were randomly assigned to experimental and control groups and underwent pre- and posttests. Using two-sample and paired T-tests, results show that students under the experimental group, which applied the Feynman Technique, showed higher posttest scores and learning gains than those in the control group. Hence, this study proves that the Feynman Technique can be an effective tool to improve K-12 studentsâ€™ learning, especially now given the new learning delivery modalities.