Poor academic achievement is a crisis in mathematics education. This study examined the mediating role of mathematics self-efficacy on the relationship between video-based instruction and academic achievement in mathematics among senior high school students. Through predictive research design, data from 197 respondents selected through simple random sampling were analyzed using mediation analysis. Mathematics self-efficacy does not mediate the predictor-criterion correlation, denying Social Cognitive Theory. Future studies may examine other mediating variables and employ qualitative approach to generate themes which may be considered as potential variables. Education practitioners may focus resources on strengthening students’ self-efficacy, engagement, and problem-solving skills to improve academic performance.