Kedisiplinan merupakan perilaku yang harus dikembangkan dalam diri siswa berkaitan dengan terlaksananya proses pembelajaran, pengembangan sikap responsif, dan bertanggung jawab. Namun, kenyataannya selama proses belajar didapati siswa kelas II C SD Kristen Kalam Kudus Yogyakarta kurang disiplin dengan bercerita dan berjalan saat proses pembelajaran tanpa izin guru, kurang mematuhi peraturan dan prosedur kelas serta lalai dalam mengerjakan tugas. Oleh karena itu peneliti melakukan tindakan pengontrolan tingkah laku dengan menerapkan penguatan positif berdasarkan langkah-langkah menempel papan stiker dan perilaku yang diharapkan, lalu menyampaikan perilaku yang diharapkan dan penguatan yang diberikan, serta memberikan penguatan langsung secara konsisten. Selain itu, siswa juga diberikan kesempatan mengajukan pendapat, guru mengingatkan perilaku yang diharapkan berulang-ulang, dan menanamkan dasar perilaku yang diharapkan atas ketaatan dan tangggung jawab terhadap Tuhan Yesus Kristus. Adapun penelitian yang dilakukan adalah penelitian tindakan kelas berdasarkan tahapan Pelton yang dilaksanakan selama tiga kali pertemuan belajar tanggal 2 Oktober, 4 Oktober, dan 11 Oktober 2018. Subjek dalam penelitian ini adalah siswa kelas II C SD Kristen Kalam Kudus Yogyakarta. Instrumen penelitian yang digunakan adalah lembar observasi check list, umpan balik mengajar, dan jurnal refleksi peneliti. Berdasarkan hasil perbandingan pertemuan pertama dan pertemuan ketiga disimpulkan bahwa penerapan penguatan positif dapat meningkatkan kedisiplinan belajar siswa kelas II C SD Kristen Kalam Kudus Yogyakarta. Hal ini dibuktikan dengan hasil data duduk rapi dari 56,25% menjadi 82,35 meningkat 26,1%, tidak bercerita dari 43,75% menjadi 82,35 meningkat 38,6%, hand signal dari75% menjadi 82,35% meningkat 7,35%, one voice on stabil 100%, dan ketepatan mengumpulkan tugas dari 68,75% menjadi 82,35% meningkat 13,6%./ Discipline is a behavior that must be developed in student related to the learning process, the development of responsive attitude, and responsibility. However, during the learning process there was a lack of discipline found in students grade II C Kalam Kudus Christian Elementary School in Yogyakarta while chatting and walking during the learning process without teacher’s permission, break the rules and procedures and neglectful in doing assignment. Therefore, researcher activated behavioral control by implementing positive reinforcement based on the steps of attach the sticker board with the expected behavior, then explain the expected behavior and reinforcement, and also provide consistent direct reinforcement. Beside that, students are also given the opportunity to give opinion, the teacher reminded the expected behavior repeatadly, and cultivated the expected basic behavior for aiming the obedience and responsibility for Christ. This research used Classroom Action Research method based on Pelton stages during three meetings on 2 nd , 4 th, 11th of October 2018. The subject is students grade II C at Kalam Kudus Christian Elementary School Yogyakarta. The instruments are checklist observation sheet, teaching feedback, and researcher reflective journal. The result of comparison between first and third meeting found the implementation of positive reinforcement can increase grade II C students’ learning discipline at Kalam Kudus Christian School Yogyakarta. As proven there are increased neat sitting data 56,25% became 82,35% increased 26,1%, not chatting data 43,75% became 82,35% increased 38,6%, hand signal 75% became 82,35 increased 7,35%, one voice on data on at maximum consistency, and the accuracy of submitting assigment 68,75 became 82,35% increased 13,6%.