Abstract This study examines five variables posited to drive(s) initial phonological transfer of (part of) one system over another in an L3: language status (L1/L2), facilitation, global structural similarity, dominance, and bilingual experience. Specifically, we investigate production of intervocalic voiced stops by English/Spanish bilinguals at the initial stages of L3 Brazilian Portuguese (BP) or Italian. These segments surface as [−continuant] in BP, Italian, and English but are realized as [+continuant] in Spanish; English transfer is therefore facilitative while Spanish is non-facilitative. Three groups (English-dominant heritage Spanish speakers, L1 English/L2 Spanish, L1 Spanish/L2 English) enrolled in first semester BP or Italian completed delayed repetition tasks in all three languages. The majority of participants across groups produce Spanish-like [+continuant] segments, suggestive of a primary role for global structural similarity. For the subset of participants across groups that produces English-like/L3-like [−continuant] segments, debrief data indicate a potential relationship between metalinguistic knowledge and [−continuant] production.