Parents play a major role in supporting children’s attitudes and behaviours towards physical activity. Enhancing parents’ physical literacy could potentially have positive impacts to the physical activity and health of themselves and their children. An online-based intervention programme designed to improve parents’ physical literacy was thus implemented in Hong Kong. The intervention included six 60-minute parent workshops, spanned over three months, that were delivered over Zoom. Each workshop included a “knowledge” and an “exercise” session, led by the investigators and trained coaches, respectively. The effectiveness of the intervention was evaluated using a quasi-experimental trial. Parents from 224 families registered to take part in the intervention and were considered the experimental group. Another 220 parents who did not sign up for the study were invited to complete two sets of questionnaires, and they were considered as the control group. Intervention effects were evaluated based on pre-to-post changes in parents’ and children’s physical activity measured using wrist-worn activity trackers, and parent-reported co-activity behaviours and physical literacy. Results based on linear mixed models suggested that the two groups did not differ in terms of objectively-measured physical activity. However, parents in the experimental group reported more positive changes in terms of co-physical activity with children, and their own physical literacy. The results suggest the intervention could improve parents’ physical literacy, but may not be sufficient to enhance activity behaviours of them and their children. Modifications to the intervention, such as including components to target children specifically, could potentially increase the impact of the programme. Due to the online-delivery mode, there is also strong potential to scale-up the designed programme to reach more parents in future initiatives.