Green seaweeds, which constitute a significant portion of the global seaweed population, exhibit a wide range of therapeutic properties. The study aimed to isolate a (1 → 4) linked sulfated rhamno xyloglucuronan, designated as UFP-2, from the edible green seaweed Ulva fasciata Delile, and to evaluate its efficacy in modulating immune responses and inhibiting infection by the SARS-CoV-2 Delta variant. Anti-inflammatory potential of UFP-2 was demonstrated through the regulation of key cytokines involved in inflammatory responses triggered by viral infections, including interferons (IFN-α/γ), interleukin (IL-1β/12/33), and tumor necrosis factor (TNF-α). Confocal microscopy and flow cytometry analyses indicated downregulation of IFN-α and IL-1β, while TNF-α expression reduced from 29.28 % in lipopolysaccharide (LPS)-induced CALU-1 cells to 1.6-5.4 %, upon UFP-2 treatment. Treatment with UFP-2 at 125 μg/mL significantly downregulated the overexpression of IL-1β level in SARS-CoV-2-infected CALU-1 cells. Administering UFP-2 to SARS-CoV-2 (delta variant) induced cells led to a higher cycle threshold (Ct) values (20.34), indicating reduced viral load, with viral copy numbers decreasing from over 6.5 × 10