DNA vaccines have been developed against viruses for many years. For COVID-19, acid nucleic immunization has been evaluated. A few preclinical studies have shown that the combination of the spike and nucleocapsid proteins of SARS-CoV-2 induced a robust immune response. In this work, we designed a plasmid that codifies for fusion proteins and evaluated its ability to elicit an immune response in a mouse model. Using in silico approaches, we determined the most immunogenic regions of the spike (S) and nucleocapsid (N) proteins of the SARS-CoV-2 Omicron strain. Once the sequences were selected, we generated the structure of this fusion protein in AlphaFold and determined its physicochemical and immunogenic properties on several platforms. The sequence was cloned in pcDNA3.1 and named pcDNA3.1/O-SN. The expression of plasmid was evaluated by Western blot and immunofluorescence. Then, BALB /c mice were immunized with 25 µg of pcDNA3.1/O-SN and parental vector pcDNA3.1. Three doses at 20-day intervals were administrated. After immunization, bleedings were performed, serum samples were obtained, and the humoral response was determined. Splenocytes were obtained from the immunized mice, and the cellular T-cell response was analyzed by flow cytometry. Finally, a cross-reaction with RBD from different SARS-CoV-2 variants of concern was evaluated. Specific antibody responses of IgM and IgG against N and S1 proteins from SARS-CoV-2 were observed in pcDNA3.1/O-SN-immunized mice. Furthermore, these antibodies exhibited neutralization activity, and production of IFN-γ was detected in CD4+ and CD8+ cells from the pcDNA3.1/O-SN-immunized mice. Additionally, a sera cross-reaction was observed with different VOCs. Our results indicate that DNA vaccination with the pcDNA3.1/O-SN generated by our working group is capable of inducing a specific humoral and cellular immune response.