Mathematical creative thinking ability of elementary school students in Padang is still low. This is due, among other things, to the learning that is still dominated by the teacher, students are still focused on the way taught by the teacher and have not been able to solve the problem properly and creatively. To overcome this problem, learning process is used through an open-ended approach. This study aims to determine the effect of the open-ended approach on students' mathematical creative thinking skills. This type of research is quasi-experiment. The population of this study is all students of grade V elementary school in Padang city, registered in group IV Padang Timur sub-district in the first semester of the academic year 2017/2018. Sample selection is done by random sampling. The experimental class is VA class students at SD Negeri 23 Marapalam and as a control class are fifth-grade students of SD Negeri 20 Air Camar, Padang city. The research instrument is a prior ability test and a test in the form of mathematical creative thinking skills. Data analysis was carried out using two-way t-test and ANAVA for interaction. The results of the analysis show that: (1) students' creative thinking ability taught with the open-ended approach is better than students taught with conventional learning. (2) The ability to think creatively of high and low students taught with an open-ended approach is better than students taught with conventional learning. (3) There is no interaction between learning through an open-ended approach and prior ability to students'mathematical creative thinking abilities.