Recently, second language (L2) instruction has benefitted from the development of instructional technology such as synchronous computer-mediated communication (SCMC). The present study was conducted to investigate learner perception of the effectiveness of SCMC interactions for L2 learning and building intercultural competence. Students (n = 55) from three different universities in Korea, Japan, and Taiwan participated in a joint online class for one semester. The purpose of the class was to facilitate students' development of linguistic and intercultural competence by interacting with peers from different cultures online. This study set out to examine the relation between learner perception and interactional features during group discussions. A range of data collection instruments were employed, including a questionnaire to track change in learner perception over time, interviews, and transcripts of interactions during each chat session. Results from linear mixed effect models suggest that among various interactional features, the following two variables were found to be significant predictors of positive attitudes towards SCMC: the amount of students' attention to language and cultural issues during online discussion. Findings are discussed in light of developing effective SCMC-based language courses.