This qualitative research investigates the practice of lurking among English as a second language (ESL) learners in a Facebook group discussion. Lurking is a term used to describe the activity of following and observing any online discussions or activities without contributing to the discussions. Lurkers are often accused of being invisible and passive participants. Facebook groups with international members usually uses English as the medium of communication in their group discussions. It is a norm for L2 learners to lurk in the group. These L2 learners often do not have the required English language proficiency and the confidence to participate actively in the group they join. This study explores lurking behaviours of three participants in learning English in informal Facebook contexts. This study uses a qualitative case study. The study involved three L2 learners who were university students and members of a Facebook group. The study involved online observation and semi-structured interviews with these three participants. Their Facebook accounts and a common Facebook group were observed for 14 weeks, and after the online observation, the participants were interviewed. Data collected from online observation and semi-structured interviewed were analysed and managed using Atlas.ti 7. The study reveals five emerging themes such as that lurkers have poor online communication skills, lack of confidence, learning by lurking, lack of a sense of belonging and lurking is the norm of Facebook groups.