As global interest in quantum mechanics grows, its inherent complexities continue to pose challenges for effective instruction. This study investigates the impact of Quantum Interactive Learning Tutorials (QuILTs) on enhancing conceptual understanding of quantum mechanics among preservice physics teachers in Korea. The QuILTs, consisting of pretests, tutorial worksheets, and post-tests, targeted the following five key concepts: possible wave functions, bound/scattering states, time evolution of wave functions, quantum measurement, and the uncertainty principle. To assess conceptual change, the Quantum Mechanics Survey (QMS) was administered to 20 preservice teachers before and after the completion of QuILTs instruction to assess conceptual change. Additionally, embedded quizzes and interviews provided deeper insights into persistent misconceptions. Results indicated a moderate to substantial overall improvement, with a Hake gain of 0.54. Significant gains were observed in understanding possible wave functions and time evolution, although challenges remained in areas such as normalization of free particle wave functions and interpretation of scattering states. Misconceptions related to quantum measurement and the uncertainty principle showed partial improvement. The findings demonstrate the effectiveness of QuILTs in enhancing conceptual understanding among preservice teachers, suggesting that research-based, concept-focused instructional strategies can support future educators in mastering complex quantum mechanics concepts. These results offer valuable insights into the development of teacher preparation curricula and instructional strategies in Korea.