Purpose: NDM-1-producing Citrobacter portucalensis and Citrobacter freundii simultaneously occurred in a hospital. This study aims to characterize the bla(NDM-1)-carrying plasmids in these Citrobacter strains. Methods: Cf7303, Cf7308, and Cf7313 were recovered from three patients in a teaching hospital from September 24 to October 1, 2021. Bacteria were identified by MALDI-TOF mass spectrometry, and antibiotics susceptibility tests were determined by VITEK (R) 2 compact system. Whole-genome sequencing (WGS) was performed using the HiSeq Illumina and QNome platform to characterize the genomes. Results: Cf7303 was identified as C. portucalensis Sequence Type 328 by WGS, and harbored two plasmids, namely pCf7303 and a novel lncFIB pNDM-Cf7303 on which antibiotic-resistant genes (bla(TEM-1), bla(CTX-M-14), bla(NDM-1), aac (3)-IId, aadA2, fosA3, sul1, sul2, catA2, tetD, dfrAl2, qacEdeltal, mph(A), and ble(MBL)) are located. C. freundii strain Cf7308 and Cf7313 belonged to the same Sequence Type 98. Cf7308 contained two plasmids, pCf7308, and an lncN1 pNDM-Cf7308 with homology to pNDM-BTR in E. coli and pNDM-CWHOO1 in C. freundii. Conclusion: We characterized a putatively novel lncFIB plasmid carrying bla(NDM-1) in C. portucalensis. In addition, the closely related bla(NDM-1)-carrying lncN1 plasmids in E. coli and C. freundii suggest that interspecies or intraspecies horizontal transfer occurs in China.