<b><i>Introduction:</i></b> Recombination-activating gene (<i>Rag</i>) 1 and <i>Rag2</i>, which are essential in V(D)J recombination, play a crucial role in B- and T-cell maturation. <b><i>Method:</i></b> We investigated the effects of <i>Rag2</i> deficiency in clustered regularly interspaced short palindromic repeats/Cas9-mediated FVB-<i>Rag2</i> knockout (KO) and wild-type (WT) mice infected with mouse adenovirus type 1 (MAV-1) via the intranasal route. <b><i>Results:</i></b> MAV-1 infection caused more severe histopathological changes in FVB-<i>Rag2</i> KO mice than in WT mice. FVB-<i>Rag2</i> KO mice exhibited moderate to severe inflammation on day 4 and severe inflammation on day 8 post infection. In contrast, WT mice showed mild inflammation on day 4 and mild to severe inflammation on day 8 post infection, including interstitial pneumonia and inflammatory cell infiltration in the lungs and liver. Viral loads in the spleen and kidneys were significantly higher in FVB-<i>Rag2</i> KO mice than in WT mice on day 8 post infection. Levels of cytokines and chemokines, including macrophage inflammatory protein-1α, induced protein 10, interferon (IFN)-α, IFN-γ, and tumor necrosis factor alpha, were upregulated in the spleens of FVB-<i>Rag2</i> KO mice compared with those of WT mice. The upregulation of several cytokines occurred concurrently with the histopathological changes. MAV-1 infection induced more severe systemic infection in FVB-<i>Rag2</i> KO mice than in WT mice. <b><i>Conclusion:</i></b> In mice, <i>Rag2</i> deficiency induces inflammatory cell recruitment via the upregulation of cytokine and chemokine levels. The MAV-1 infection model can be utilized to assess the efficacy and safety of therapeutic agents for human adenoviral diseases.