SARS-CoV-2-IN-60 (compound 5a) is an S-adenosylmethionine (SAM)-competitive and irreversible SARS-CoV-2 nsp16-nsp10 methyltransferase activity inhibitor with an IC 50 of 9 μM and a K i of 26 μM. SARS-CoV-2-IN-60 can specifically occupy a newly identified pocket adjacent to the SAM-binding site on nsp16. SARS-CoV-2-IN-60 has the potential for pan-coronavirus therapeutics.