The purpose of this study is to investigate the effects of interaction between two mobile chatting conditions, voice-chatting and text-chatting, on speaking and writing performance. Forty-four students taking two College English classes participated in the present study. They were divided into two different experimental groups: voice-chatting and text-chatting groups. Both groups took pre-tests for speaking and writing tasks from TOEIC. During the semester, they carried out the same speaking activities on various topics via voice-chatting or text-chatting. Participants paired up and communicated in two different modes with given tasks such as describing a picture, responding to questions, and expressing an opinion. Post-tests were administered at the end of the semester. The major findings of the study were as follows: First, significant differences were found in terms of speaking and writing performance in both groups. Participants in the voice-chatting group, however, did not significantly show improvement in their performance in the writing task, expressing an opinion. Second, different types of chatting on mobile devices did not have any influence on students’ speaking or writing performance after practicing different tasks. Lastly, mobile chatting provided a stimulating environment to actively participate in class and also increased time for students to practice speaking and writing. It can be concluded that employing mobile chatting is effective in improving learners speaking and writing performance and it motivates students to be interested in learning. Pedagogical implications and future studies will be discussed.