Canine mammary tumor (CMT) are the second most common tumor in dogs. Exosomes can act as biomarkers for the early diagnosis of tumors, and also be involved in the pathogenesis and metastasis mechanism of tumors. The expression profile of exosomal RNA revealed that there were a total of 5547 differentially expressed mRNAs, and 196 differentially expressed lncRNAs. GO and KEGG enrichment analysis found that the differentially expressed mRNAs and lncRNA target genes were associated with metabolic processes, DNA replication, cell proliferation, cell junction, and cell adhesion. In conclusion, this study revealed lncRNA and mRNA expression profiles in exosomes derived from plasma of CMT and further annotated their potential functions. The data obtained in this study will also provide valuable resources for understanding lncRNA information in plasma exosomes of dogs with CMT, and contribute to the study of early diagnostic markers and pathogenesis of CMT.