Every classroom environment reflects the cultural features of the country where it is located. In this study, with a focus on cultural features, we compared the science classroom environments of two Asian countries: Korea and Thailand. For this, What Is Happening In this Class (WIHIC) and the Cultural Learning Environment Questionnaire (CLEQ) were administered to 1575 students (765 from Korea and 810 from Thailand) in Grades 4, 6, 8, and 10. The results of two instruments were analyzed and discussed with a particular focus on the four cultural dimensions in science classrooms, which were reframed from Hofstede's four cultural dimensions. The results of the analysis can be summarized as follows. First, regarding the first dimension, relationships between individuals and groups, students in both countries liked collaborative activities and had many emotional exchanges in their classrooms. However, cognitive collaborative activities occurred more frequently in Thailand than in Korea. Second, regarding the second dimension, equity issues, almost all students in Korea perceived that they participated equally in science classrooms. However, in Thailand, students thought they had equal participation in science classrooms except for the gender aspects. That is, Thai boys and girls were reported themselves to be participating in different ways in their classrooms. Third, regarding the third dimension, relationships between students and teachers, two kinds of relationships were investigated: teacher authority and teacher support. In terms of teacher authority, the extent of psychological distance between students' and their teachers' power was similar in the two countries. However, in terms of teacher support, Thai students had more positive perceptions about teacher support than Korean students did. Fourth, regarding the features of science teaching and learning processes, Korean students had more negative perceptions of involvement, investigation, and task orientation than Thai students did. The negative responses of Korean students could be the cause of the low engagement of Korean students in their science classrooms. Based on these results, educational implications are discussed in terms of culturally appropriate pedagogies in science classrooms.