<p>Viral diseases pose a persistent global threat, necessitating next-generation antiviral strategies that overcome the limited antiviral spectrum, rapid resistance, and insufficient immune engagement of conventional therapeutics. Herein, a carrier-free, “drug-delivering-drug” antiviral nanocomplex, termed BBTS25, is developed through directed self-assembly of baicalin and the bioactive peptide TS25. BBTS25 exhibits potent broad-spectrum antiviral efficacy. Notably, in a representative viral model, it strongly suppresses viral replication, reducing intracellular and supernatant viral loads by approximately 70% and 80%, respectively, while concurrently compromising virion structural integrity. Mechanistically, atomistic molecular dynamics simulations reveal that BBTS25 efficiently penetrates cellular membranes, with its peptide component forming strong interactions with intracellular nucleic acids. The interaction shields nucleic acids from nuclease-mediated degradation, thereby sustaining the activation of the type I interferon pathway. Consistently, transcriptomic profiling of treated cells shows robust induction of interferon-stimulated gene networks and activation of innate antiviral responses. In vivo, BBTS25 administration in a lower vertebrate (teleost) model enhances survival by approximately 47% and demonstrates excellent biocompatibility. Furthermore, spleen transcriptomic analysis and quantitative PCR indicate that BBTS25 activates dendritic cells and macrophages, and promotes type I interferon-associated immune responses. This work establishes a broadly applicable strategy for next-generation host-directed antiviral intervention via self-assembly of poorly soluble natural compounds and unstable bioactive peptides.</p> Graphical Abstract <p></p>