There is a consensus among researchers and educators that teachers’ language register (LR) influences learners’ cognitive development. While previous studies have examined how teachers’ professionalism in relation to LR is evaluated by educational experts and researchers, this study was motivated by the need to understand the perceptions of parents, teachers, and teacher-trainees regarding the contribution of LR to teachers’ professionalism in intercultural environments. In this mixed-methods study, 308 participants were asked to rate teacher professionalism based on one of three written reflections, identical in content but differing in LR level. The study was conducted in Israel, a multilingual society in which Hebrew is the official language of instruction but is a second language for many teachers and learners. This context, shaped by ongoing immigration, adds an important cultural lens to the investigation. Unlike previous studies, the findings in this research showed that very few participants considered LR an important component of teacher professionalism. Instead, they emphasised proficiency in other areas, particularly teacher knowledge, cultural awareness, and responsiveness to learners’ needs. This study offers global implications for teacher education in increasingly multicultural and multilingual societies, suggesting that perceptions of professionalism prioritise cultural competence and pedagogical adaptability over formal linguistic norms.