Worldwide spread of antibiotic resistance genes among Enterobacteriaceae isolates is of great concern. F33:A−:B− plasmids are important vectors of resistance genes, such as bla _CTX-M-55/-65 , bla _NDM-1 , fosA3 , and rmtB , among E. coli isolates from various sources in China. We determined and compared the complete sequences of 17 F33:A−:B− plasmids from various sources. These plasmids appear to have evolved from the same ancestor by mobile element-mediated rearrangement, acquisition, and/or loss of resistance modules and similar IncN1, IncI1, and/or IncX1 plasmid backbone segments. Our findings highlight the evolutionary potential of F33:A−:B− plasmids as efficient vectors to capture and diffuse clinically relevant resistance genes.