The legitimacy of non-native speaker English teachers as professional English educators has long been debated. While recognizing these teachers’ multilinguality can partly counter the prevalence of native-speakerism, it may also present identity challenges for them, particularly when they teach in multilingual contexts where they may not share their students’ linguistic backgrounds, or where their own language(s) could be perceived as a cultural threat. In these contexts, critically examining how language ideologies intersect identity construction has the potential to recognize/problematize challenges that might have remained unnoticed/normalized in dominant discourses. Focusing on one such situation, in this study we explored how a group of mainland Chinese English teachers working in Hong Kong schools experienced this identity challenge. Our sources of data included a narrative survey completed by a total of 21 teachers and semi-structured interviews with 10 of them. Thematic analysis revealed that many of these teachers – primarily native speakers of Putonghua (the national language of China) with limited knowledge of Cantonese (the dominant language in Hong Kong) – believed that using their Putonghua or accented Cantonese while teaching English may project them as less competent. Despite recognizing the potential benefits of incorporating these languages to enhance students' English learning, they strictly adhered to English-only instruction, not only to conform to institutional and societal expectations, but also to conceal their linguistic markedness and safeguard their professional legitimacy. This chain of language ideological inclinations can act as part of broader forces that foster the dominance of so-called native English and undermine the legitimacy of non-native speaker teachers. The study highlights the role of language ideologies in constraining teachers’ professional identity construction and in perpetuating linguistic hierarchies and social inequities. Supporting language teachers in developing their critical language awareness could afford them alternative ideological orientations, which may empower their teacher identity (re)construction.