Antibiotic resistance poses a major global health threat, necessitating new approaches to treat bacterial infections. We isolated bacteria from the brown macroalgae Sargassum swartzii collected along the Indian coast. Of 279 isolates, 47.6% showed antibacterial activity against Staphylococcus aureus and Vibrio parahaemolyticus when screened. Ten potent isolates underwent analysis of biosynthetic gene clusters and 16S rRNA sequencing. Isolate MP-99 carried polyketide synthase (pks) and non-ribosomal peptide synthetase (nrps) genes and exhibited antibacterial effects. 16S rRNA sequencing and species-specific markers confirmed the isolate MP-99 as Bacillus paralicheniformis. Gas chromatography-mass spectrometry revealed major components N-hydroxy methyl acetamide and dichloroacetic acid, 6-ethyl-3-octyl ester. The extract exhibited broad-spectrum antibacterial activity against Klebsiella pneumoniae, Vibrio parahaemolyticus, and methicillin-resistant Staphylococcus aureus (MRSA). It also potently inhibited biofilm formation by MRSA and V. parahaemolyticus at sub-microgram concentrations. Molecular docking suggested selective binding of certain isolate compounds to biofilm-associated proteins. The B. paralicheniformis extract showed moderate toxicity in an Artemia salina lethality assay. In conclusion, the marine isolate Bacillus paralicheniformis PMRU2.6 extract has promising antibacterial and antibiofilm potential against pathogens, warranting further research to develop safe therapeutic applications.