We report for the first time the occurrence of integrative conjugative elements (ICEs) in Riemerella anatipestifer ( R.anatipestifer ) isolated from diseased ducks in China. For this purpose, a total of 48 genome sequences were investigated, which comprised 30 publicly available R. anatipestifer genome sequences, and 18 clinical isolates genomes sequences. Two ICEs, named ICE Ran RCAD0133-1 and ICE Ran RCAD0179-1 following the classic nomenclature system, were identified in R. anatipestifer through the use of bioinformatics tools. Comparative analysis revealed that three ICEs in Ornithobacterium rhinotracheale showed a high degree of conservation with the core genes of ICE Ran RCAD0133-1, while 13 ICEs with high similarity to ICE Ran RCAD0179-1 were found in Bacteroidetes . Based on the definition of ICE family, ICE Ran RCAD0179-1 was grouped in CTn DOT/ERL family; however, ICE Ran RCAD0133-1, which had no significant similarity with known ICEs, might be classified into a novel ICE family. The sequences of ICE Ran RCAD0133-1 and ICE Ran RCAD0179-1 were 70890 bp and 49166 bp in length, had 33.14 and 50.34% GC content, and contained 77 CDSs and 51 CDSs, respectively. Cargo genes carried by these two ICEs were predicted to encode: R-M systems, IS elements, a putative TonB-dependent receptor, a bacteriocin/lantibiotic efflux ABC transporter, a tetracycline resistance gene and more. In addition, phylogenetic analyses revealed that ICE Ran RCAD0179-1 and related ICEs were derived from a common ancestor, which may have undergone divergence prior to integartation into the host bacterial chromosome, and that the core genes co-evolved via a related evolutionary process or experienced only a low degree of recombination events during spread from a common CTn DOT / ERL family ancestor. Collectively, this study is the first identification and characterization of ICEs in R. anatipestifer ; and provides new insights into the genetic diversity, evolution, adaptation, antimicrobial resistance, and virulence of R. anatipestifer .