Recent global health emergencies have led to significant considerations for preventive health behaviors (PHBs). Given the severity of these crises and the significance of protection against the spread of diseases, understanding the predictors of engaging in PHBs is very important. Therefore, this study investigated the effect of social media usage on self-efficacy, perceived threat, and PHBs among adults in Malaysia. Along with social media usage, this study further investigated the effects of self-efficacy and perceived threat on PHBs. The Health Belief Model (HBM) was used as the theoretical basis of this study. An online survey was administered among adults aged 18 years and above. A total of 275 usable online survey was collected through purposive sampling technique. The findings revealed that social media usage positively affects self-efficacy and perceived threat. The results also showed that perceived threat had the strongest effect on PHBs, followed by social media usage, and self-efficacy. Implications and suggestions for future studies were also discussed.