The purpose of this study was to develop an indicator of core competency of freshmen of an Institute of Science & Technology (IST). Through the document analysis and the expert survey, core competency indicators that include 5 core competencies and 15 sub-competencies (a total of 48 items) were developed. Then content validity was examined by experts in measurement and statistics and secondary education. Also, by using students’ responses, reliability was tested with Cronbach’s alpha and construct validity were tested through confirmatory factor analysis. Results suggest that the core competency indicator is reliable and valid in measuring core competencies of freshmen students in an Institute of Science & Technology. Discussions were provided in terms of improving student admission processes.