Mitochondrial membrane permeability pore opening is recognized as a molecular mechanism involved in programmed cell death. The purpose of this study was to evaluate the effects of certain fractions crude aqueous extract of the root bark of Plumbago zeylanica (PZ) on the opening of the mitochondrial membrane permeability transition pore in rat liver. Pore opening, mitochondrial ATPase activity, lipid peroxidation and liver function markers were assessed spectrophotometrically while caspase 9 activity and liver morphology were monitored by immunohistochemistry and histology respectively. All fractions of PZ induced pore opening and enhanced the activity of caspase-9. Significant increases were observed in the mitochondrial ATPase activity while the level of malondialdehyde was significantly reduced. Sinusoidal dilation and hypertrophy were observed in liver sections of treated rats. These results suggest that aqueous fractions of PZ have bioactive agents capable of altering mitochondrial bioenergetics and inducing the opening of MMPT pore with mild hepatotoxicity.