Purpose: The purpose of this study is to describe university students' motivations for using Facebook as an informal learning tool and explore the key barriers that may inhibit learning on the social media platform. Design/methodology/approach: A case study approach was adopted in this study. Participants were 82 university students who participated in "e-Tutor" -- an informal learning activity, conducted through Facebook. Focus group interviews were conducted, and students' interactions on Facebook were also analysed to understand their motives for using the social media platform for learning. The uses and gratifications theory was used to explore student motivations for participating in the learning activity. Findings: Results suggest that students perceived Facebook as a potential tool for learning and identified multiple motivating factors for their participation that included information seeking, convenience, connectedness, entertainment and reward seeking. Results also show that time constraints, social anxiety and cultural issues may inhibit learners' active participation on social media platforms such as Facebook. Originality/value: This study outlines an approach to use readily available and low-cost technological tools in learning design and provides some insights for teachers to design ubiquitous and personalised learning environments for students using such technologies, particularly social media. Specifically, Facebook offered a way to engage students in informal learning which can supplement students' formal learning trajectories at university. While the uses and gratifications students sought through Facebook had an overall positive effect on their participation in e-Tutor activity, certain barriers can impede student active participation in learning environments on social media sites such as Facebook.