The present study was aimed to evaluate the anticonvulsant activity of 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose (PGG) isolated from methanolic leaf extracts of Mangifera indica in mice. Anticonvulsant activity of PGG was evaluated against pentylenetetrazole (PTZ)-induced and maximal electroshock (MES)-induced convulsions in mice. Additionally, locomotor activity and GABA levels in the brain were estimated to explore the possible CNS-depressant activity and mechanism behind the anticonvulsant activity, respectively. In these studies, PGG (2.5, 5, and 10 mg/kg, intraperitoneal (i.p.)) showed significant and dose-dependent inhibition of PTZ and MES-induced convulsions. Furthermore, PGG administration showed significant decrease in the locomotor activity as an indication of its CNS-depressant property; also, PGG has significantly increased the GABA levels in the cerebellum and whole brain other than the cerebellum. In conclusion, PGG isolated from M. indica showed potent anticonvulsant activity, and possible mechanism may be due to enhanced GABA levels in the brain.