Social media platforms are increasingly used to disseminate social marketing messages about mental health and wellbeing. This study presents a range of message appeals used in social media enabled mental health promotion and stigma reduction messages. Furthermore, it examines the relationship between the type of message appeals and audience engagement. A content analysis of 65 organisation-generated YouTube videos about depression and anxiety and stigma reduction was conducted. The most utilised message appeal was Sorrow, followed by Affiliation, Ease/Convenience, Hope, Humour, Guilt/Shame, Heroic/Successful, and Fear. Multiple regression analysis was used to examine the relationship between the type of message appeals and audience engagement in terms of the number of likes, comments, and shares. The analysis revealed that Sorrow is the most useful message appeal for generating audience comments. However, Sorrow is negatively associated with the number of likes and shares. The results suggest that mental health promotion messages may engage a larger audience through Affiliation and Hope as they have a positive impact on the number of shares. This could, in effect, turn audiences into vocal advocates for mental health promotion and stigma reduction messages.