Abstract: The research aims at exploring the implementation of constructivism through Problem Based Learning to enhance students achievement. This is a classroom action research that employ 4 steps (1) planning, (2) acting, (3) observing, and (4) reflecting. The results showed that teacher and students activities are apropriate with Problem Based Learning, consisting of orientation to the problem, learning organisation, individual/group investigation, presentation and evaluation. Teacher and studentsâ perceptions to the method were positive, and the students learning outcomes improved significantly.  Abstrak: Tujuan penelitian ini adalah untuk mengetahui penerapan pendekatan konstruktivistik melalui metode problem based learning untuk meningkatkan prestasi belajar siswa di SMK Muhammadiyah 2 Malang. Penelitian ini tergolong penelitian tindakan kelas (Classroom Action Recearch)  dengan tahap (1) planning (perencanaan), (2) acting (pelaksanaan), (3) observing (pengamatan), dan reflecting (refleksi). Hasil penelitian menunjukkan bahwa aktivitas guru dan siswa telah sesuai dengan mekanisme problem based learning, yaitu orientasi pada masalah, organisasi belajar, penyelidikan individu/kelompok, menyajikan hasil karya dan evaluasi. Persepsi guru dan siswa  terhadap metode Problem Based Learning adalah positif, dan prestasi belajar siswa meningkat.