This study aimed at finding out the effect of Treffinger creative learning model with RME principles on creative thinking skills by controlling numerical ability. This study was conducted to the fifth grade students of elementary schools in Manggarai regency using post-test only control group design of experiment. This study involved 101 fifth grade students as sample who were selected by using random sampling technique. The instruments were numeric ability test and creative thinking skill test. Data were analyzed by using ANCOVA aided by SPSS 23.0 program. The results showed that (1) the creative thinking skill of the students who learned mathematics Treffinger creative learning model with RME principles was higher than those who learned mathematics through conventional model, (2) the creative thinking skill of the students who learned through Treffinger creative learning model with RME principles was higher than those who learned through conventional learning model, after controlling numeric ability, (3) numeric ability gives a 33.2% contribution to the students' creative thinking skill. These findings show that Treffinger creative learning model with RME principles has a significant effect on the students' creative thinking skill. Mathematics teachers are suggested to employ this model in developing students' creative thinking skill.