The purpose of this research was to determine whether the present Korean teacher education programs for secondary science teachers are effective in improving the teacher conceptions of constructivism and STS. It is because the current Korean National Science Curriculum is consistent with both ideas as reforms. The teacher education programs sampled in the research included pre-service programs and two types of in-service programs. These two were the Qualifying In-service Program and the Iowa Korean Science Teachers Workshop. The Iowa Program was considered as an experimental program emphasized the constructivist perspective. Specially designed questionnaires for identifying teacher conceptions before and after the programs were administered. The conceptions about constructivism and STS improved as a result of the instruction in both of the pre-service and in-service teacher education programs. The pre-service program was more effective than the in-service programs in improving the teacher conceptions of both constructivism and STS. The Qualifying Inservice program was less effective than Iowa Korean Science Teachers Workshop. It was necessary for inservice programs for Korean secondary science teachers to be more emphasized on constructivism and STS. Iowa Korean Science Teachers Workshop provided a possible example to design a new special in-service program focused on constructivist perspectives as a way of aligning the Korean National Science Curriculum more quickly with recommended teaching practices in Korean schools.