This research seeks to compare the effectiveness of the Problem-Based Learning (PBL) model with that of the Discovery Learning (DL) model in enhancing students’ learning outcames. The study was conducted with Grade XI learners at SMA Negeri 1 Siantar and utilized a quantitative method through a quasi-experimental design. Data were obtained through a post-test consisting of five essay items assessing cognitive learning outcomes. The instrument’s validity and reliability were assessed through product–moment correlation and Cronbach’s Alpha procedures. The results of the study showed that students taught using the PBL (Problem-Based Learning) model achieved higher average scores (mean = 74.26, SD = 14.29) than those taught using the discovery learning model (mean = 65.52, SD = 15.91). The t-test findings revealed a meaningful difference between the two groups (tₕ = 2.51 > tₜ = 1.995, α = 0.05). This result indicated that Problem Based Learning outperforms Discovery Learning in improving students’learning outcames