Although DNA vaccines hold significant potential, their practical application in aquaculture remains limited. In both mammals and teleost fish, B cells, which recognize antigens and produce antibodies, play an important role in immunity. In this study, B-cell epitopes capable of inducing fish immunity from IS701 family transposase (IS701) and molybdopterin-dependent oxidoreductase (Mol) proteins of Nocardia seriolae were screened. PcDNA-IS701 and pcDNA-Mol recombinant plasmids were constructed. The results showed that two proteins possessed multiple B-cell epitopes, and both pcDNA-IS701 and pcDNA-Mol induced innate immunity and specific antibody responses, along with increased mRNA expression levels of genes encoding humoral (MHCIIα and CD4) and cell-mediated (MHCIα and CD8α) immunity. In addition, both pcDNA-IS701 and pcDNA-Mol strengthened the protection against N. seriolae infection, with immune protection rates of 45.06 % for IS701 and 61.04 % for Mol, respectively. In conclusion, pcDNA-IS701 and pcDNA-Mol are candidate DNA vaccines for nocardiosis in fish.