Although the paradigm shift towards English as an International Language (EIL) has been generally accepted within the academic community, a valorization of native speaker norms continues to be prevalent among many non-native speakers (NNSs). Through data drawn from a qualitative questionnaire and proficiency assessment results (TOEIC), this mixed methods study investigates the degree to which native speaker models of communicative competence affect the linguistic self-confidence (LSC) and performance (LP) of 83 Japanese employees of a large, international corporation. Although the results were inconclusive for the latter inquiry, they show that participants who lack experience using English in international contexts have a greater tendency to valorize Native Speaker norms, a belief which, in turn, negatively affects their linguistic self-confidence and attitudes towards the target language (TL). Supplementary data were also collected by interviewing the participants in person or by e-mail in order to discern deeper insights into this particular psycho-linguistic phenomenon, and responses indicated that employees with greater experience using English for their work were much more articulate in explaining or justifying the reasons for their attitudes towards native-speaker norms.