This study aims to improve mathematics learning outcomes using peer tutoring models through problem possing in grade IVA students of SD Muhammadiyah Jogodayoh, Sumbermulyo, Bambanglipuro, Bantul.This research was conducted at SD Muhammadiyah Jogodayoh, Sumbermulyo, Bambanglipuro, Bantul. This research is a classroom action research. The research subjects were all students of class IVA SD Muhammadiyah Jogodayoh, Mulyodadi, Bambanglipuro, Bantul totaling 28 students with 12 male students and 16 female students. The object of this research is the peer tutor model through problem possing. CAR steps include planning, implementing, observing and reflecting. Collecting data in this study by observation or observation, response questionnaires and achievement tests and interviews. The results showed that the use of peer tutoring models through problem possing could improve mathematics learning achievement for grade IVA students at SD Muhammadiyah Jogodayoh, Sumbermulyo, Bambanglipuro, Bantul. During the research, the results of the first cycle of student achievement questionnaires with an average percentage of 71.42% (less successful category) then increased in the second cycle with an average percentage of 85.71% (very successful category) above 80%.