The purpose of this study is to explore learners' perceptions on Schema-Based Instruction (SBI) for teaching the polysemous English prepositions ("in", "on", and "at"). SBI is a form of instruction based on the insights of cognitive linguistics and is a way of vocabulary learning and teaching, which provides learners with the schematic core meaning. The SBI has been expected to contribute to polysemous word learning, which is different from conventional ways of teaching polysemous words that most often offers learners a list of several prepositions and their corresponding meanings. The present study focuses on investigating learners' perception, which is indispensable for discussing the effectiveness of instruction. A questionnaire was conducted with 56 Japanese university students after the SBI and a practical experience to use core meaning. Data were analyzed qualitatively to extract constructs that learners possess on SBI, especially on core meaning. Based on the results, the effective points of core meaning in SBI perceived by learners consisted of applicability, efficiency as a learning method or tool, and practical for distinguishing between the use of prepositions. However, due to reasons such as insufficient understanding, there were learners who negatively perceived core meaning and learners who could not determine the effectiveness of core meaning. Although most learners in this study received a positive impression on core meaning with one-shot instruction, this research revealed that learners recognized the needs of continual training or exercise to make use of core meaning in their English using or English learning context.