Engagement plays an important role in students' success in learning. While learner engagement has been widely examined, the degree to which learners engage in online learning and the relationship between online engagement and learning outcomes, particularly in the domain of second/foreign (L2) language learning, still remain under-explored. To bridge the gap, this study examined college L2 English learners' profiles of online engagement and their learning outcomes. A total of 85 first-year college students participated in this study. The results showed that college students' online L2 English learning engagement is multidimensional, including behaviroral, cognitive, affective, and social facets. Additionally, students' actual behavioral (e.g., task engagement time and task completion rate) and self-perceived online engagement (e.g., behavioral, cognitive, and affective online engagement) are significantly correlated. Nonetheless, among the two levels of online engagement measures, only task score in the actual behavioural engagement is a positive predictor of students' learning outcomes. The study concludes with practical implications for online teaching.