This research aims to examine the role of second-language (L2) phonology in third-language (L3) acquisition. As a mean to assess the degree of influence of the L1 accent and L2 accent in L3 production, an experiment that involved the judgment of a foreign accent was developed. Two groups of native English speakers [(i) five who had not learned any language other than Korean, and (ii) five who had learned Japanese before learning Korean] produced Korean sentences, and 25 native Korean-speaking raters identified each production according to the speaker’s dominant accent, either English or Japanese. The results revealed that native English speakers who had learned Japanese before learning Korean were more frequently identified as having a strong Japanese, rather than English, accent in their Korean production. In accounting for the results, several hypotheses were discussed, including language distance (typological proximity), inherently different mechanisms for foreign language acquisition as compared with the natural acquisition of the L1, psycho-affective factors, and stronger links between foreign languages in the speaker’s mind. The findings of this study provide further evidence for the claim that L2 exerts an influence on L3 accent; however, this interference is reduced with an increase in L3 proficiency