This study investigated the anti-respiratory syncytial virus (RSV) mechanism of Callicarpae Nudiflorae Folium(CNF) extract based on the p38 mitogen-activated protein kinase/nuclear factor kappa B (p38 MAPK/NF-κB) signaling pathway. In vitro, the cytopathic effect assay was employed to evaluate the anti-RSV activity of CNF, with the selectivity index (SI) as the primary indicator. In vivo, an RSV-infected mouse model was established to assess the anti-RSV effects of CNF by monitoring lung index, lung viral load, histopathological changes in lung tissue, and secretion levels of inflammatory cytokines, including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). The mRNA expression of genes associated with the p38 MAPK/NF-κB pathway was analyzed using RT-qPCR, and protein expression was detected via Western blot. In vitro studies demonstrated that CNF possesses anti-RSV activity, with SI of 12.10 and IC₅₀ of 26.10 µg/mL. In vivo results showed that RSV infection significantly increased the lung index in mice. Compared to the model group, the CNF group exhibited a notable reduction in lung index and lung viral load, along with alleviated histopathological changes in lung tissue, including decreased alveolar wall thickening and reduced infiltration of lymphocytes and neutrophils. Furthermore, CNF group significantly lowered the secretion levels of pro-inflammatory cytokines TNF-α and IL-1β and downregulated the mRNA and protein expression of p38 MAPK, p65 NF-κB, and inhibitor of nuclear factor kappa B alpha (IκBα). These findings suggest that CNF exerts anti-RSV effects, likely through immunomodulatory and anti-inflammatory mechanisms mediated by the p38 MAPK/NF-κB signaling pathway.