Virtual-reality 3D modeling helps primary school students to develop creative thinking and problem-solving skills. Through hands-on practice, students can understand abstract concepts more intuitively, and can realize the combination of theory and practice. However, in conventional virtual 3D modeling teaching, students often lack immersive modeling experience, and the modeling method may not be in line with the cognitive way of thinking of primary school students, which, in turn, causes high cognitive load. Immersive virtual reality (IVR) environments provide students with more immersive and intuitive interactions, which can help promote students’ cognitive, emotional, and social development. Therefore, this study combined IVR with 3D virtual modeling to form an immersive virtual-reality-based 3D modeling approach (IVR-based 3D modeling) and designed a quasi-experiment to compare it with the conventional virtual reality 3D modeling approach (CVR-based 3D modeling) to explore its effectiveness. The results of the study show that the IVR-based 3D modeling approach significantly enhanced elementary school students’ creative thinking, including its sub-dimensions (e.g., challenge, imagination, and curiosity), when compared to the CVR-based 3D modeling approach. The same conclusion was reached for problem-solving skills. IVR-based 3D modeling also reduced students’ cognitive load during the learning process, especially in terms of mental effort. The results of the interviews complement the experimental results, and the learners’ perceptions of the new approach explain the experimental results to some extent.