This study investigated novel instructional approaches for tackling ongoing obstacles in students’ understanding of algebraic expressions. Particularly, this research aimed to examine the effectiveness of Contextualized Problem-Based Learning (CPBL) approach in improving the performance of Grade 7 learners in solving problems involving algebraic expressions at Diffun National High School for School Year 2025–2026. Applying quasi-experimental non-equivalent pretest-posttest control group design, purposive sampling was used to determine two intact classes to be assigned into experimental and control groups. The statistical tools used were frequency count and percentage, mean, standard deviation, paired samples t-test, independent samples t-test, Levene’s test, Shapiro-Wilk test, and Cohen’s d. Pretest was administered prior to the implementation of the intervention then, right after the intervention, the posttest was administered. Outcomes uncovered that the control group gained slightly higher mean score (74.76%, SD = 6.72) than the experimental group (71.52%, SD = 7.79); however, the difference was not statistically significant (t = -1.734, p = 0.088). Within-group analysis revealed that the experimental group improved significantly from pretest to posttest (mean gain = 2.99; t = -2.531, p = 0.016), indicating CPBL’s favorable effect on student learning. Cohen’s d value of -.442 indicates that the participants in the control group showed a higher mean gain than the participants in the experimental group.