In response to the call for integrating a praxis orientation to understand processes of language development through active engagement with teachers and learners, this article introduces techno-reflective narrative interview (TRNI) as a tool to understand how learners invest in their English as a second language (ESL) language and literacy practices as social practices in English medium instruction (EMI) courses. It is timely in integrating both technical and critical guidance for methodological innovations in the field of applied linguistics. To illustrate how this aim is achieved, this article first justifies the significance and theoretical basis of TRNI by elaborating on the definitions of and underpinning rationale for it, followed by the relationship among second language (L2) learners, investment, and TRNI. It then discusses the methods adopted by the 69 most cited empirical studies from Google Scholar that used the model of L2 investment as the theoretical model and compares these methods with TRNI. Finally, it discusses how TRNI was developed and adopted in two action research projects conducted by the author and two lecturers among local undergraduate students in the Hong Kong context. Through these steps, I demonstrate how TRNIs can be adopted or adapted to provide an interactive space for ESL learners to reconstruct and perform their English speaker and learner identities, share their learning experiences with the agency to introduce their positions, voices, and stories, and therefore, claim legitimacy as English users in EMI courses. Copyright © 2024 Elsevier Ltd. All rights reserved.