This research reveals the improvement of Indonesian students’ mathematical problem solving skill taught by problem-based learning with realistic model. Experimental research design was used and the population of the research was junior high school grade VIII students of Muhammadiyah 25 in Rantau Prapat Indonesia. Two classes with 30 students in experimental class I and 30 students for experimental class II were chosen as the sample of the research. Moreover, data found from pretest and postest of experimental class I and II were collected and calculated by Gain Hake pattern. The finding of the research showed that students posttest result after having taught by implementing problem-based learning with realistic media was 82, 08, and students taught by conventional teaching strategy was only 76,35. Furthermore, based on Gain pattern analysis, problem solving skill of experimental class I was higher with 0,61 than students taught by implementing conventional teaching strategy with only 0,46. Then, based on t-Test it was found that students’ problem solving skill with tobserved= 3,961 and t table = 2,00. In other words, t observed> t table, 3,961 > 2,00. This research conluded that students’ problem solving skill was higher when they were taught by problem-based learning with realistic media.