Parmotrema perlatum lichen is traditionally used as a spice in Indian households and also to treat diseases such as eczema, respiratory diseases, pulmonary diseases, and arthritis. This study emphasizes the extraction of secondary metabolites from foliose lichen P. perlatum with antioxidant and antibacterial activity. The secondary metabolites extracted from P. perlatum using hexane, chloroform, and methanol were analysed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS/MS) shows that P. perlatum extracts possess 2,4-dihydroxy-3,6-dimethyl-methyl ester, 1,4-benzenediol, atraric acid, orcinol, benzoic acid, 2,5-dimethyl- resorcylic acid, and savinin, tetrahydroterotri-L- glutamate, primidolol, ustiloxin, mallotinic acid, and mecambrine. The efficacy of three solvent extracts of lichen against Gram-negative bacteria Pseudomonas aeruginosa, Chromobacterium violaceum, and Gram-positive Lactobacillus plantarum was tested. The methanol extract of P. perlatum has the highest antibacterial activity against the tested bacteria at a concentration of 10 mu g/ml as compared with the other two solvent extracts. The antioxidant potential of P. perlatum was determined using ferric ion reducing antioxidant power, 2,2-diphenyl-1-picrylhydrazyl, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), and nitric oxide scavenging activity assays, which exhibit that all extracts showed radical scavenging potential. Kalpasi, Lichen, Antibacterial, Antioxidant, GC-MS, LC-MS, Secondary, metabolites, phenolic constituents, acid, Energy & Fuels, Engineering