The current study explores the effects of different types of voice-based chat on EFL students’ negotiation of meaning according to proficiency levels. Participants included 123 Korean university students of English. They were divided into two voice-based chat groups: student-student voice-based chat and student-chatterbot voice-based chat. The experiment was administered throughout one semester, 16 weeks. Negotiation of meaning evident in the chats was coded for confirmation check, comprehension check, clarification requests, repetition, and reformulation, and was measured by counting the number of meaning negotiation moves. Important findings were as follows: Firstly, there were significant differences between the first chat and the last chat. The mean frequencies of negotiation moves at all proficiency levels positively changed over time as a result of participating in student-chatterbot voice-based chat. Particulalry, student-chatterbot voice-based chat, as compared to student-student voice-based chat, allowed students to use more negotiation strategies, and the strategies used in the chats also appeared to be different according to the students’ proficiency levels. Lastly, positive perceptions of voice-based chat were observed at all proficiency levels. This study provides empirical evidence to substantiate the effects of voice-based chatterbots in oral interaction. Based on the findings, pedagogical implications are made on the effective implementation of voice-based chatterbots in EFL contexts.