To minimize the spread and fear of COVID-19, the South Korean government disclosed detailed location-based information about confirmed cases. Information regarding the confirmed cases was then maliciously distributed on social networking services (SNS). Few studies have investigated how the fear of COVID-19 and the disclosure of information in confirmed cases affect intention on online behavior, despite SNS being a space where people can express themselves with high social support. An online survey was conducted in South Korea. People who feared contracting COVID-19 had a negative perception of not only self-disclosure but also information disclosure by others. However, the perceived online social support could overcome the fear of infectious diseases and encourage active engagement to disclose information. The disclosure of information about confirmed cases impacted social support and self-disclosure intentions. This study contributes to the literature on information disclosure for public health purposes in the online environment during the fear of the epidemic. The world government and future social media platform companies should develop a specific process of information disclosure to manage the fear of public behavior.