This study investigated the tendency of overpassivization of unaccusative verbs by Korean learners of English as a foreign language (FL). Sixty Korean native college students participated in the study, along with 17 English-speaking counterparts serving as a comparison group. Consistent with the findings of previous research, this study found Korean students' tendency to incorrectly accept passive-voice with inanimate subjects. The results of this study highlighted the role of lexical animacy, the hierarchy of agentivity, and language-specific effects on FL judgment. The findings of this study suggest a robust language-specific L1 effect on L2 acquisition and a greater involvement of cognition in FL use than language input.