The outbreak of COVID-19 pandemic since the last days of 2019 has led to school closure worldwide and forced institutions at all levels to move to online or distance learning. This study was conducted to explore university students’ readiness to such a sudden situational shift to online learning. We surveyed 1304 online-learning students in a higher education institution in Vietnam. Through exploratory factor analyses, we identified three dimensions of online learning readiness (OLR): online learning motivation, online learning self-efficacy beliefs, and online self-directed learning. We then conducted multiple regression analyses to investigate the predictive power of different students’ individual characteristics and perceptions on OLR, and the impacts of the three OLR dimensions on students’ intention to use online learning (IU). Our results suggested that students’ perceived facilitating conditions and their online learning experience were the significant predictors of OLR. Furthermore, online learning motivation was the construct that exerted the strongest influence on IU, compared to other OLR constructs. The study highlights the need for improving facilitating conditions to support students’ OLR. It also suggests enhancing the usefulness and enjoyment that students perceive from online learning to improve their willingness to use this learning channel.