Seaweed extract is being used as an organic biostimulant in agricultural and horticultural crops to reduce chemical fertilizers. This research aimed to determine the importance of seaweed liquid fertilizers (SLFs) derived from Sargassum sp. when given exogenously to black gram (Vigna mungo L.) under saline stress, and growth characteristics were analyzed in the laboratory. The morphological and biochemical characteristics of the plants were studied at the vegetative stage of 30 days after infusion of saline stress (50, 100, and 150 mM, NaCl) and SLF (5 %, 10 %, and 15 %) for five days. Our findings demonstrated a substantial stimulatory effect on black gram growth characteristics. The most effective treatment was a 10 % SLF concentration, which improved the morphology, chlorophyll pigments, RWC, proline, and protein content of black gram under salt stress. The finding was confirmed by LC-MS analysis of seaweed liquid fertiliser, which revealed the presence of growth regulators (alpha-Tocopherol, Isocorydin, 5,6-Dihydroxy-3′,4′-dimethoxyflavanone, Alloxanthin, 6,7,3′,4′-Tetrahydroxyflavanone, Flavanomarein, 3-Hydroxyechinenone, and Zeaxanthin). Thus, these SLF from Sargassum sp. might be exploited as a promising biostimulant in plants that are under abiotic stress, perhaps leading to more ecologically friendly agricultural practices in the future.