SARS-CoV-2, the virus causing COVID-19, has been extensively studied to find effective antiviral treatments. Cyclosporine A (CsA), an immunosuppressant, has been suggested to inhibit coronaviruses, but its mechanism remains unclear. This study reveals that SARS-CoV-2's non-structural protein 1 (Nsp1) hijacks the CsA-suppressed NFAT signaling pathway to enhance viral replication. Nsp1 interacts with calcineurin A (CnA) to displace RCAN3, a regulatory protein that inhibits CnA activity, thereby activating NFAT. Activated NFAT promotes the expression of DDX5, a cellular protein that facilitates viral replication. The study also shows that calcineurin inhibitors like CsA and VIVIT inhibit SARS-CoV-2 replication and exhibit synergistic antiviral effects when combined with nirmatrelvir. The findings elucidate the molecular mechanism by which CsA inhibits SARS-CoV-2 replication and the anti-viral action of calcineurin inhibitors. Nsp1 is a crucial viral protein that enhances viral replication by activating NFAT and DDX5. The study demonstrates that Nsp1 overexpression can partially reverse the suppression of SARS-CoV-2 replication by CsA. The results highlight the role of Nsp1 in SARS-CoV-2 replication and the potential of calcineurin inhibitors as antiviral agents. The study also shows that the combination of calcineurin inhibitors with nirmatrelvir has a synergistic antiviral effect against SARS-CoV-2. The findings provide new insights into the mechanisms of SARS-CoV-2 replication and the potential of calcineurin inhibitors as antiviral treatments.SARS-CoV-2, the virus causing COVID-19, has been extensively studied to find effective antiviral treatments. Cyclosporine A (CsA), an immunosuppressant, has been suggested to inhibit coronaviruses, but its mechanism remains unclear. This study reveals that SARS-CoV-2's non-structural protein 1 (Nsp1) hijacks the CsA-suppressed NFAT signaling pathway to enhance viral replication. Nsp1 interacts with calcineurin A (CnA) to displace RCAN3, a regulatory protein that inhibits CnA activity, thereby activating NFAT. Activated NFAT promotes the expression of DDX5, a cellular protein that facilitates viral replication. The study also shows that calcineurin inhibitors like CsA and VIVIT inhibit SARS-CoV-2 replication and exhibit synergistic antiviral effects when combined with nirmatrelvir. The findings elucidate the molecular mechanism by which CsA inhibits SARS-CoV-2 replication and the anti-viral action of calcineurin inhibitors. Nsp1 is a crucial viral protein that enhances viral replication by activating NFAT and DDX5. The study demonstrates that Nsp1 overexpression can partially reverse the suppression of SARS-CoV-2 replication by CsA. The results highlight the role of Nsp1 in SARS-CoV-2 replication and the potential of calcineurin inhibitors as antiviral agents. The study also shows that the combination of calcineurin inhibitors with nirmatrelvir has a synergistic antiviral effect against SARS-CoV-2. The findings provide new insights into the mechanisms of SARS-CoV-2 replication and the potential of calcineurin inhibitors as antiviral treatments.