Studies on teacher education have given increasing attention to pedagogical content knowledge (PCK): the knowledge necessary for teaching specific content as a theoretical construct. As a component of the teacher's professional knowledge base, orientations toward teaching science (OTS) are critical to developing the PCK needed for inquiry-based science teaching. However, there is a lack of understanding about the relationships between OTS and the content to be taught and OTS and students' education levels. This study explored the OTS of 86 first-year Thai preservice teachers with different majors upon their entry into a science teacher education program. Their pedagogical orientations were measured with the existing Pedagogy of Science Teaching Test. The results revealed that most preservice teachers' OTS are between the "active direct" and the "guided inquiry". There was no significant relationship between their OTS and the subject matter; however, there was a relationship with the students' education levels. For instruction at the secondary level, the preservice teachers' OTS were less likely to be inquiry-based. A qualitative analysis of the written justifications indicated that the preservice teachers' perceptions of students' ways of learning influenced their pedagogical tendencies. This suggests that the participants perceived that the students' education levels would influence their learning strategies. Therefore, for preservice science teachers to develop inquiry-based OTS and PCK, teacher education should emphasize on how students best learn science to achieve scientific literacy.