Phonological awareness is the stepping-stone to learning to read as it helps children map language sounds onto letters. Theories of bilingualism posit that phonological awareness is a language-common literacy skill. However, bilingual learners are also thought to build language-specific representations. To illuminate common and specific dual-language processes, we asked bilingual Spanish-English heritage language speakers (N = 60, M[subscript age] = 8.2) to complete a phonological sound-matching task in Spanish and English during functional Near Infrared Neuroimaging (fNIRS). The left perisylvian activation was common across bilinguals' two languages, including similar active regions and functional connections. The findings further revealed language-specific modulation of the system with more robust engagement of the temporal networks for Spanish and frontal networks for English. We interpret the results in the context of analytically demanding reading experiences in English and more informal home-based Spanish language experiences typical of heritage language speakers.