MDR Klebsiella pneumoniae ST307 is a high-risk clone, whose genetic features contribute to its adaptation to hospital environments and the human host. This study describes the emergence and clonal dissemination of K. pneumoniae ST307, recovered during November 2018 to February 2019 in a hospital in Buenos Aires city, which concurrently harbored KPC-3 and NDM-1. These isolates were resistant to all β-lactams and to the ceftazidime/avibactam combination. Molecular studies showed that bla_KPC-3 was located in Tn4401a platform, while bla_NDM-1 was surrounded upstream by ISKpn14 followed by a partial sequence of ISAba125 and downstream by bleMBL-trpF, located in a 145.5 kb conjugative plasmid belonging to the Inc A/C group. The dissemination of K. pneumoniae ST307 isolates co-producing KPC-3 and NDM-1 could lead to a worrisome scenario due to the remarkable features of this clone and its resistance profile.