Building interpersonal connections in asynchronous online learning is important, but it is harder to achieve compared to face-to-face learning experiences due to its mostly text-based nature. Facebook is a popular social media platform and has been used as an outside-class communication space in formal learning contexts to supplement cognitive and affective aspects of learning. In this study, we used Facebook groups as supplemental social spaces in two asynchronous online master's-level courses to understand if it impacted students' perceptions of social presence (i.e., copresence, immediacy, and intimacy), learning interaction with faculty and peers, as well as sociability of the online learning environment. The results indicated that students felt more positively about social presence and learning interactions with other classmates and their instructor and perceived the course as having more sociability after they joined the class Facebook group. Findings have implications for supporting social impression formation in online learning.