Mathematical representation is an important skill in mathematics learning that enables students to interpret and solve problems with ease. However, building confidence in such a skill can be difficult for some students, especially for those who lack self-motivation skills. Therefore, this study examines the effects of the think-talk-write strategy and the expository strategy on students' abilities in mathematical representation in order to understand the relationship between mathematical representation and self-efficacy. In this study, a Quasi-Experiment design comprising the experiment group and the control group was applied. Learning process by Think-talk-write (TTW) strategy was implemented in the experiment group only. On the other hand, the learning process in the control group was accomplished without the TTW strategy. The sample in this study comprised students of the eighth grade studying geometry and spatial relations at a public junior high school. For the purpose of this study, two groups were created: 1) an experimental group, in which the think-talk-write strategy was employed, and 2) a control group, in which the expository approach was applied. In addition, mathematical representation ability and self-efficacy scale tests were used as the instruments of this quasi-experimental study.