Introduction: The COVID-19 pandemic has caused massive school closures worldwide and many schools were forced to adopt online teaching mode. Purpose: This survey study aims to examine the effectiveness of online teaching in physical education (PE) and support needed from the teachers’ perspective. Methods: Responses from 294 frontline PE teachers were collected via an online survey between 4 and 29 January 2021. Results: Four major findings were highlighted in our study. First, most teachers reported that online PE lessons were not effective to improve motor skill acquisition and physical activity level, the major reasons for which were “lack of practical training”, “students’ lack of learning motivation/interest”, and “limited interpersonal interactions”. Second, most teachers encountered difficulties in online teaching, with major difficulties comprising “limited interpersonal interactions’ and “difficult to retain students’ learning motivation/interest”. Third, most teachers felt that online teaching was stressful due to the increased workload in preparation and safety concerns of the home-exercise programme. Fourth, many teachers suggested that schools or governments should provide online teaching kits, such as suggested online lesson plans or home activity recommendations, for their reference. Conclusions: In summary, the effectiveness of online teaching in PE during COVID-19 school closures was generally perceived to be low and difficult by the frontline PE teachers. Schools and governments should provide sufficient support, such as online teaching kits and concrete teaching guidelines, for PE teachers to develop creative and interactive online lessons, which will in turn benefit students in motor skill acquisition and physical activity level. Copyright © 2021 JPES.