<![CDATA[Mathematical concept mastery at the elementary school level is still frequently hindered by one-directional learning approaches, where students tend to be passive throughout the learning process. This condition creates an urgency for implementing innovative learning models capable of fostering active engagement while simultaneously strengthening conceptual understanding. This study was designed to examine the extent to which the Project Based Learning (PjBL) model combined with leaflet media can impact students' mathematical concept understanding at the elementary school level. The method employed was quantitative with a quasi-experimental nonequivalent control group design, involving two class groups—one as the treatment group (PjBL + leaflet) and the other as the comparison group (conventional learning). Data collection was conducted through descriptive tests that had been validated in terms of validity, reliability, difficulty level, and discriminating power. Analysis included normality tests, homogeneity tests, N-Gain, and independent sample t-test. Data revealed a surge in the treatment group's mean score from 61.45 to 82.95, with an N-Gain of 0.57 (moderate category). In contrast, the comparison group only obtained an N-Gain of 0.17 (low category). Hypothesis testing yielded a significance value of 0.000 (p < 0.05), which statistically confirms a significant effect of PjBL implementation assisted by leaflet media. These findings provide empirical evidence that the integration of project-based visual media is substantively superior to conventional methods in building mathematical concept understanding among elementary school students. ABSTRAK Penguasaan konsep matematis di tingkat sekolah dasar masih kerap terhambat oleh pendekatan pembelajaran yang bersifat satu arah, di mana peserta didik cenderung pasif dalam proses belajar. Kondisi ini memunculkan urgensi penerapan model pembelajaran inovatif yang mampu mendorong keterlibatan aktif sekaligus memperkuat pemahaman konseptual. Studi ini dirancang untuk menguji sejauh mana model Project Based Learning (PjBL) yang dipadukan dengan media leaflet dapat memberikan dampak terhadap pemahaman konsep matematis siswa sekolah dasar. Metode yang digunakan adalah kuantitatif dengan rancangan quasi-experimental nonequivalent control group, melibatkan dua kelompok kelas satu sebagai kelompok perlakuan (PjBL + leaflet) dan satu lagi sebagai kelompok pembanding (pembelajaran konvensional). Pengumpulan data dilakukan melalui tes uraian yang telah tervalidasi dari sisi validitas, reliabilitas, tingkat kesukaran, dan daya beda. Analisis mencakup uji normalitas, homogenitas, N-Gain, dan independent sample t-test. Data menunjukkan lonjakan nilai rata-rata kelompok perlakuan dari 61,45 menjadi 82,95, dengan perolehan N-Gain sebesar 0,57 (kategori sedang). Sebaliknya, kelompok pembanding hanya memperoleh N-Gain 0,17 (kategori rendah). Uji hipotesis menghasilkan nilai signifikansi 0,000 (p < 0,05), yang secara statistik mengonfirmasi adanya pengaruh nyata dari penerapan PjBL berbantuan leaflet. Hasil ini memberikan bukti empiris bahwa integrasi media visual berbasis proyek secara substantif lebih unggul dibandingkan metode konvensional dalam membangun pemahaman konsep matematis siswa di jenjang sekolah dasar.]]>
