Flipped-classroom learning has been shown to improve students' learning experience and performance in tertiary education. However, few studies have been done in Asia where the learning culture is vastly different from the West. Here, we studied the effect of flipped-classroom learning with the use of interactive videos on the academic performance of a group of first year undergraduate physics students in Hong Kong. By employing a concept-based pre-test and post-test, normalized gains of 35% and 13% were obtained for the flipped and control class, respectively. A very strong correlation (r = 0.72, p < .001) was shown between the post-test score and the exam results of the flipped class, while the control class showed a moderate positive correlation (r = 0.37, p = .013). Our results showed that the conceptual knowledge of students taught in flipped-classroom improved significantly more than the students taught traditionally, and that their understanding in conceptual knowledge served as a stronger indicator of their exam performance. The interactive videos were well-received and were shown to be one of the most valued components by the students.