In recent, mobile technology is experiencing a highly development, it is necessary to explore whether it holds the potential to boost EFL learners’ language acquisition based on its instant messaging apps in synchronous voice chat (SVC) mode. With a focus on Chinese EFL learners, this study aimed to compare their speaking performance in SVC and face-to-face (F2F) chat modes. It also explored the relationship between learners’ speaking performance and anxiety levels in these two chat modes which allow real-time communication. In this mixed methods study, WeChat instant messaging was used as the platform for SVC. Forty students from a public university in China participated in 4 chat sessions in SVC and F2F chat modes over 4 weeks. Quantitative data were collected through the oral scores of the participants’ performance in the chat sessions and anxiety questionnaires. Then, qualitative data were obtained from a focus group interview. The findings revealed a significant difference in learners’ speaking performance in SVC and F2F chat. Students’ speaking performance outperformed in SVC chat compared to F2F chat. This could be linked to students’ anxiety levels which were slightly higher in F2F chat. Despite that, most of the students preferred F2F chat to SVC chat due to the practicality of F2F chat.