Background: Emotional appeals in health-related advertising can increase public interest. However, only limited research exists concerning emotional appeals in advertising on social media and with regards to stroke. This study explored which type of advertising appeal achieves a greater audience engagement with the Stroke Riskometer mobile app. Methods: Facebook users with Android OS aged 20+ living in the Czech Republic were exposed to Facebook advertising campaigns between 29/Jul/22-18/Aug/22. Using a Facebook split test experiment tool, users were randomly assigned to one of the three message appeals - humour, fear and identification. Message appeals were pretested in discussions with Facebook users. Data were analysed using a Facebook ads manager with the Click-through-rate as a standard main outcome. Results: 56100 users viewed advertisements (75% aged 55+; 60% women) and 2008 clicked (65% by women, 86% were >55 years,). Fear vs humour vs identification had a 3.9% (95%CI 3.6-4.2) vs 3.0% (95%CI 2.7-3.2) vs 2.8% (95%CI 2.5-3.0) click-through-rate. Conclusions: This study on emotional appeals in health-related advertising on social media demonstrated that fear-based advertising led to the largest number of clicks to download the Stroke Riskometer app. Our results add to the limited evidence on the effectiveness of the fear appeal in health-related Facebook campaigns (e.g., about hypertension, smoking, drink driving). Our fear-based ads also provided better results when compared to previous ads that didnt use emotional appeals (e.g. 2.6% Click-through-rate for lung cancer prevention). Our results provide an insight into the use of emotional appeals in order to maximise user engagement in health-related social media advertising.