Learning science is the most exciting part of being a high school student. The fun learning through exploration and laboratory experiments is the best part of science. This study aimed to test the effectiveness of the heuristic approach with the teacher-made worksheets as a teaching innovation in distance learning in helping the respondents to understand the topics of General Biology 2. This research employed a mixed- method; the qualitative data were evaluated using the phenomenological technique, while the quantitative data were processed using the Statistical Package for Social Sciences version 25 (SPSS v.25). The researcher used a pretest, five teacher-made worksheets, a posttest, and a delayed posttest as tools. Also, focus group discussion was considered to find out the common problems encountered by the students and the researcher himself. All the gathered data was recorded digitally and through field notes and discreetly handled. There are 10 enrolled students in Science, Technology, Engineering, and Mathematics (STEM) during the school year 2020–2021, and they were all chosen purposefully. This study involved the five-week topics in the second semester of the 3rd quarter. Results revealed an increase in the respondents' learning performance based on the mean percentage scores of the posttest. Based on the increase in the mean of the delayed posttest, the innovation promotes retention for the students. The researcher and the students had technical problems because of a power outage and unstable internet connections. Still, respondents face the challenges of output management and helping their parents first before learning. There is a significant difference in the respondents' performance before and after implementing the innovation. The heuristic approach to teaching improved the performance of the STEM students at San Felipe High School under the subject General Biology 2. It is recommended that teachers use the heuristic approach to teach students how to work in a digital world.