BACKGROUND: Social media has been a common platform to disseminate health information by government officials during the COVID-19 pandemic. However, little is known about the determinants of public engagement in officials' posts on social media, especially during lockdown. OBJECTIVES: This study aims to investigate how the public engages in officials' posts about COVID-19 on social media and to identify factors influencing the levels of engagement. METHODS: A total of 511 adults aged 18 or over completed an online questionnaire during lockdown in Iraq. Levels of engagement in officials' posts on social media, trust in officials and compliance of government instructions were assessed. RESULTS: Fear of COVID-19 and trust in officials were positively associated with compliance of government instructions. Trust in officials was also associated with active engagement in officials' posts on social media, including commenting, posting and sharing of the posts. CONCLUSIONS: Trust in government has been established during the COVID-19 pandemic. Public engagement in officials' posts is crucial to reinforce health policies and disseminate health information.