This study focuses on a COVID-19 disinformation video promoting hydroxychloroquine as a cure, while dismissing other promoted COVID-19 preventive behaviours. It examines the virality of the video among Nigerians, their convictions on claims made, and likely behaviour in the possibility of suspected COVID-19 infection. The study was premised on the “availability cascade effect” which predicts a higher tendency for people to believe viral information, especially when supported by individuals considered experts on the issue being promoted. It adopted the survey research method, using snowball sampling. Data for the study was gathered electronically online from 222 participants who responded to survey. The snowball sampling method was adopted due to movement restrictions in Nigeria occasioned by the ravaging COVID-19 pandemic at the time of data collection. Findings from the study show that over 90 percent of respondents were aware of the video, with many denying further sharing online. Despite multiple fact-checks on different claims in the video, respondents who still believed the claims were found more likely to try-out hydroxychloroquine efficacy as a COVID-19 cure than those who do not. Respondents were however mostly positive on adhering to promoted COVID-19 preventive measures despite the contrary claims in the video. The virality of the video compared to its fact-checks, and sustained belief in its promoted disinformation claims, support the need to stop false information from spreading very early. Hence, there must be sustained efforts to continuously track false and malicious claims in the public space and strive to stop its spread immediately.