The world is going through the scourge of COVID-19 pandemic since last several months. The pandemic appears to be less severe in highly Dengue endemic countries. Furthermore, COVID-19 in two elderly patients (with no evidence of Dengue virus (DV) infection) elicited antibodies that gave false-positive results in DV serological tests. We anticipated that SARS-CoV-2 and DV share antigenic similarity and performed molecular docking studies. Our computational modelling studies predicted that human anti-DV antibodies can indeed, bind to RBD of SARS-CoV-2 Spike protein. Some of these interactions can also potentially intercept human ACE2 receptor binding to RBM. Our computational analysis showed that m396 Ab (against SARS-CoV-1) did not dock with RBM of SARS-CoV-2, a fact already proven experimentally. This confirmed reliability and robustness of our approach. So, immunological memory to DV in endemic countries is thwarting COVID-19. Available Dengue vaccines can be repurposed against SARS-CoV-2 in DV non-endemic countries until approved vaccines/ antivirals become available against COVID-19. Based on the observations that COVID-19 and Dengue severity maps do not tend to overlap and the fact that serological cross-reactivity has been reported for COVID-19 antibodies with Dengue antigen (s), together with results from our computational studies, it is imperative that serology-based diagnosis should be complemented with NAT/virus antigen detection-based tests for definitive diagnosis of either disease in regions where both of these viruses are now co-existent. Furthermore, we still do not know whether antibodies to SARS-CoV-2 will hinder/ameliorate DV infections by binding to DV particles and reduce dengue incidences in the future or, augment DV infection and severity by means of antibody-dependent enhancement (ADE).