Abstract Online language learning communities play an important role in providing learners of Chinese as a second language (CSL) with access to authentic language opportunities to communicate with native speakers of Chinese. However, few studies have examined CSL learners’ self-initiated naturalistic interactions with native speakers of Chinese on such platforms. This current study aims at filling this research gap by examining five East Asia CSL adult learners’ interactions with native speakers of Chinese in an informal learning context on an instruction-oriented social-networking based learning community. Adopting Henri’s (1992) analytic framework to understand the interactions between online learners from both cognitive and social dimensions, it finds that different types of interactions with native speakers of Chinese influenced learners’ differently. The study provides suggestions to CSL teachers as well as educational technology designers on how to maximize the benefits of online learning communities for CSL learners in their informal language learning beyond the classroom.