The purpose of this study is two-fold. First, we explored the psychometric properties of a selfidentity change instrument that was previously developed for English learning college students in China. Second, using this instrument, we examined participants' self-identity change related to gender, major, and years of English learning. A total of 273 undergraduate students from two adjacent geographic locations (Taiwan and mainland China) participated in a paper-based survey. Exploratory factor analysis (EFA) revealed five sub-scales that were mainly consistent with the original version. However, the EFA also suggested exclusion of one item, multi-dimensionality, and room for improvement of this instrument regarding item reliability. Inferential statistics revealed that (a) students in Taiwan exhibited a higher self-confidence change as compared to their mainland peers; (b) English and bilingual science majors underwent higher change in additive and subtractive bilingualism, followed by art and humanity majors; (c) for bilingual majors, those who started learning English prior to grade 3 were better able to switch between two identities than those who started in middle school and beyond; and (d) gender is not a significant predictor of identity change. Discussion was contextualized within educational policy and practice regarding English learning and bilingual education in these two locations.