This study investigated the impact of social interactions among a class of undergraduate students on their learning engagement in a social networking environment. Thirteen undergraduate students enrolled in a course in a university in Hong Kong used an Elgg-based social networking platform throughout a semester to develop their digital portfolios and interact with each other. Student online activities were analyzed using content analysis and descriptive statistics with social network analysis. The findings suggest that the social interaction afforded by a social networking environment was short-lived, individual-centered and casual. Communication skills and autonomy on the part of students are required to foster communication. The study further revealed that while such social patterns in the social networking environment appeared to enhance social engagement, a high level of cognitive engagement was not demonstrated. Recommendations are made in relation to the effective utilization of a social networking platform to support productive and meaningful learning.