This qualitative case study explores English teachers’ perceptions of the role of L2 Persian proficiency in the L3 English learning experiences of Balochi-Persian bilingual students in Sistan and Baluchestan, Iran. Grounded in Cummins’ Interdependence Hypothesis, the study draws mainly on semi-structured teacher interviews to examine reported links between Persian proficiency, classroom comprehension, literacy transfer, learner confidence, and English learning difficulties. The findings suggest that, from teachers’ perspectives, Persian functions as an important instructional bridge through which students access English explanations, grammatical terminology, and literacy practices. However, the study does not establish direct causal effects. Rather, it identifies teacher-reported patterns indicating that weaker Persian proficiency may be associated with reduced access to English instruction, lower participation, and greater emotional difficulty in English classes. The findings point to the need for early Persian literacy support, balanced multilingual pedagogy, and careful use of Balochi as a supplementary scaffold in bilingual classrooms.