Online technologies have dramatically influenced not only formal learning, but also knowledge acquisition in a more incidental and informal manner (Gray, 2004; McFerrin, 1999; Pennington, 1989). Therefore, it is imperative to explore the impacts of internet-mediated informal learning that significantly affects one’s formal education. This study examines what EFL students, including those who do not perceive FB as helpful to their English learning, can incidentally learn. Two research questions were explored: 1. What is Taiwanese students’ perception of using FB on learning English? 2. What can EFL students informally learn through facebooking? A qualitative study was conducted. Multiple data were collected, including perceptual data and performance data. It was found that students perceived FB participation as course work, disinclination, and power negotiation. Although 45% participants perceived FB community ineffective for their English learning, this study revealed that students could informally improve their academic knowledge and skills, social and collaboration, and motivation. These findings argued that learning can occur even when meaning-making process is perceived to be meaningless to an individual. Teachers’ role is not merely to scaffold students’ formal learning, but also to create a context that can draw learners’ informal learning.