The purpose of this study was to investigate the effect of chess training on 5thgrade students’ problem solving abilities. The review of literature started with the research on novice and expert problem solvers. We then found a number of studies regarding the mathematics’ problem solving and chess training. The findings paved the way to conduct the present study. The study was experimental and we used one-group pretest-posttest design. A cluster random sampling method was used to choose 25 fifth graders from the population of all 5th grade students in the center of one of the south-eastern provinces of Iran. Cronbach Alpha coefficient was used to insure the reliability of the tests. In addition, 52 sessions of chess training was offered by one of the authors as “treatment”. The research showed that chess training had a positive and meaningful effect on the 5th grade students’ mathematical problem solving abilities. This finding could help the mathematics curriculum developers and textbook writers to use chess as an effective tool to promote students’ problem solving abilities either as extra-curricular activity or integrated with the formal school mathematics curriculum.