Three-dimensional (3D) modeling provides a suitable context for the improvement of students' higher order thinking skills as it involves challenging and complex learning tasks. For students to succeed in difficult learning tasks, it is necessary to determine the effects of the scaffolding type given to the students in the learning process. This study asserts that reflective and supportive scaffolding has a critical effect on the dependent variables. Reflective scaffolding enables students to explain their reflective processes and clarify their reflective behavior, using personal reflection as a learning tool. Supportive scaffolding provides a process to develop knowledge and guidance on what participants should consider. This study compares the effects of different scaffolding types (reflective or supportive), students' prior knowledge on students' use of metacognitive strategies, spatial ability self-efficacy, and spatial anxiety in the 3D computer-aided design course. A pretest and posttest 2 x 2 x 2 factorial quasi-experimental model was used in the study. This study was carried out with 118 undergraduate mechanical engineering students. Analysis of covariance (ANCOVA) was used in the analysis of the data. The results showed that the supportive scaffolding group scored higher in the metacognitive strategies variable than the reflective scaffolding group. The supportive scaffolding group showed higher spatial ability than the reflective scaffolding group. This study provides engineering educators with an overview of the use of scaffolding types, their effects on the effectiveness of learning environments, and the design of these environments.