The COVID-19 pandemic is a great challenge to leadership education in universities. Although previous findings provide support for the effectiveness of online learning, the impact of online leadership course on students’ learning outcomes and well-being has not been well documented. Using objective outcome and subjective outcome evaluation strategies, the present study examined students’ perceived qualities and effectiveness of an online credit-bearing service leadership course adopting asynchronous mode (primarily online learning) and synchronous mode under COVID-19. Regardless of teaching modes, the subject yielded positive impacts. Specifically, pretest-posttest (N = 228) showed that there were positive changes in students’ service leadership qualities, life satisfaction and psychological well-being. For students’ perception of the course (N = 219), results indicated that most students were positive in their learning experience and satisfied with course design, lecturer quality and the benefits of the course to their development. Students’ changes and subjective perceptions were positively correlated, but with a low effect size. The findings reflected that online service leadership course adopting asynchronous or synchronous mode was effective, and students were positive about their learning experience.