An endophytic bacterium was isolated from the surface sterilized pneumatophores of mangrove plant Avicennia marina, Vellar estuary, south east coast of India. Using 16S rRNA sequencing the bacterium was identified as Bacillus cereus –SjAM16104 with similarity of 99% and sequence has been deposited under accession number GU930360. It grew optimally at 26ºC, pH 7 and 5% of salinity. The major fatty acids of B.cereus were anteiso-15:0 (40.55%), anteiso-17:0 (17.39%), iso-16:0 (8.95%), iso-15:0 (7.82%), iso-17: 0 (6.62%), 16: 0 (5.23 %) and fatty acids iso-14:0 (2.03%), anteiso-13:0 (1.87%) were detected in small amounts. Experiments were conducted to evaluate the efficacy of endophytic B.cereus in improving crop growth of Bacopa monnieri under in vitro condition. The growth rate of endophytic B.cereus treated explants were highly significant than the control explants.