This study aims to produce a product in the form of learning module based on contextual approach that can improve the understanding of mathematical concepts on the rectangular building material. This research was using research and development method. Data were analyzed descriptively and quantitatively This research was conducted in two schools namely SMPN 22 Bandar Lampung and SMPN 8 Bandar Lampung. Further analyzed using effectiveness test, efficiency, and attractiveness, and t-test. The results showed that the average N-Gain was 0.75 (effective), the average efficiency was 1.11> 1 (high), the attractiveness was 90.5% (very interesting) and based on t-test of normalized N-gain from both schools, the resulting sign (2 tailed) value is less than 0.05, then Ho is rejected means the development of learning module based on contextual approach is an effective product in the learning process so as to improve the understanding of mathematical concepts of learners.Penelitian ini bertujuan untuk menghasilkan produk berupa modul pembelajaran berbasis pendekatan kontekstual yang dapat meingkatkan pemahaman konsep matematis pada materi bangun datar segiempat. Penelitian ini merupakan penelitian pengembangan R&D dengan tujuh langkah Borg and Gall (1989). Penelitian dilaksanakan di dua sekolah yaitu SMPN 22 Bandar Lampung dan SMPN 8 Bandar Lampung. Teknik pengumpulan data berupa kuesioner (angket) dan tes. Selanjutnya dianalisis menggunakan uji efektifitas, efisiensi, dan kemenarikan serta uji t-tes. Hasil penelitian menunjukkan bahwa rata-rata N-Gain ternormalisasi 0,75 (efektif ), rata-rata efisiensi diperoleh nilai rasio 1,11>1 (tinggi), kemenarikan 90,5% (sangat menarik) dan berdasarkan uji- t N-gain dari kedua sekolah didapatkan nilai sign (2 tailed) kurang dari 0,05, maka Ho ditolak berarti pengembangan modul pembelajaran berbasis pendekatan kontekstual merupakan produk yang efektif dalam proses pembelajaran sehingga dapat meningkatkan pemahaman konsep matematis peserta didik .Kata kunci: modul, pendekatan kontekstual, pemahaman konsep matematis.