This qualitative study examines bilingual Saudi university students’ perceptions of “untranslatable” Arabic expressions and what these perceptions reveal about the relationship between language, culture, and worldview. To address limited research on how bilingual speakers understand untranslatability, eight Master’s students from King Saud University, Riyadh were interviewed about three to five Arabic expressions they considered difficult to translate into Standard English. Participants explained the reasons for their perceptions and discussed the cultural, emotional, and pragmatic meanings that may be lost in translation. Findings indicate that many Arabic expressions contain cultural, religious, emotional, and pragmatic meanings that cannot be fully reproduced in English. Examples included expressions related to communal solidarity (الفزعة), gratitude and blessing (يعطيك العافية), honor and dignity (مويه وجه), and culturally embedded social rituals (نعيمًا). Participants emphasized that perceived untranslatability primarily results from differences in cultural context, emotional nuance, metaphorical imagery, and religious meaning rather than vocabulary gaps alone. The findings suggest that Arabic expressions often function as cultural scripts reflecting values such as hospitality, respect, solidarity, and social reputation. Translating them into English may therefore simplify or reduce their cultural and emotional depth. The study highlights the importance of cultural awareness in translation and TESOL and supports more culturally responsive approaches to bilingual language teaching.