This investigation examined the antioxidant, antimicrobial, cytotoxic, and anti-inflammatory activities of the acetone extract of the lichen Platismatia glauca (L.) W.L. Culb. & C.F. Culb. (PGAE). The phytochemical study of PGAE showed presence of seven compounds: salazinic acid, β-orcinol carboxylic acid, 3-hydroxyphysodalic acid, physodalic acid, physodic acid, atranorin, and chloroatranorin. The antimicrobial potential was determined by microdilution which showed that S. aureus was most sensitive to the effect of PGAE with MIC value 0.312 mg/ml. Antioxidant activity was evaluated by using DPPH method. The obtained IC50 value for PGAE was 194.30 ± 3.32 μg/ml. The cytotoxic effect of the extract was evaluated by MTT test and the strongest activity was towards human epithelial carcinoma cells with IC50 value of 59.10 ± 0.46 μg/ml. The findings revealed that the application of lichen extracts decreased the paw edoema in a dose-dependent manner at 1, 2, 3, and 4 h following carrageenan administration. Keywords: Platismatia glauca (L.) W.L. Culb. & C.F. Culb; Parmeliaceae; phytochemical analysis; antimicrobial activity; antioxidant activity; cytotoxic activity.