Numerous mAbs against the S protein of SARS-CoV-1 have been generated for research and diagnostic assay development. Some of these may be able to cross-react with the S protein of SARS-CoV-2 and serve as tools to aid research on this newly emerged virus. In this current study, an immunogenic domain in the S2 subunit of SARS-CoV-1 was found to be highly conserved in multiple strains of SARS-CoV-2 (Figure 1 and Table). Consistently, WB and IF analyses showed that four different mAbs generated using this SARS-CoV-1 domain were cross-reactive against the S protein of SARS-CoV-2 (Figures 2 and 3).