Salmonellosis, caused by non-typhoidal , is a common foodborne gastrointestinal infection. Third-generation cephalosporins are recommended as the first-line treatment for infections. Our study aimed to investigate the molecular epidemiology, antimicrobial resistance, and the transmission of extended-spectrum β-lactamases (ESBL) genes in 96 clinical isolates collected between 2020 and 2022 at a tertiary hospital in Shenzhen, China. We performed antimicrobial susceptibility testing and whole-genome sequencing to identify serotypes, multilocus sequence typing, antimicrobial resistance genes in these isolates, and the genetic structures of the / genes. Seventeen serotypes were identified, with . 4,[5],12:i:- (37.5%) being the most common, followed by . Enteritidis (15.63%), . Typhimurium (14.58%), London (7.29%), and Rissen (5.21%). MLST analysis revealed 19 distinct sequence types (STs), with ST34 being the most prevalent (36.46%), followed by ST11 (15.63%) and ST19 (13.54%). Antimicrobial resistance testing showed those isolates had high levels of resistance to ampicillin (72.92%) and tetracycline (71.88%), with 70.83% of isolates as multidrug-resistant (MDR). Three genes ( , and ) and were identified among 18 cefotaxime-resistant strains, of which one and 12 isolates successfully transferred or to C600 via conjugation, respectively. The / -carrying contigs in nine isolates ranged from 2,156 to 164,862 bp, were located either on the chromosome (n=1) or plasmids (IncI1, IncK1, IncA/C) (n=9), and the / genes were associated with IS. Our study demonstrates the diversity of MDR serotypes in clinical isolates, and highlights the role of plasmids and mobile genetic elements in the horizontal transfer of / , emphasizing the need for continuous surveillance of in clinical samples.