Mitochondrial Permeability Transition (mPT) pore opening is critical to cell survival. Alpha stone is used in the treatment of fibroid but the possible mechanism has not been explored. Twenty Swiss albino mice (15–18 g) were orally treated with 100, 200 and 400 mg/kg body weight (bw) dose of alpha stone daily for seven days. Mitochondria were isolated and mPT, F₁F₀  ATPase, lipid peroxidation and cytochrome c release were assessed spectrophotometrically. Similar assays were assessed in vitro. The mPT pore opened maximally with induction fold of 14 at 640 µg/ml (in vitro) and, 26 at 400 mg/kg bw (in vivo) in the absence of calcium. This was reversed in vitro in the presence of calcium. Lipid peroxidation occurred in both cases while cytochrome c release was significantly high (in vitro). Alpha stone caused the mPT pore opening both in vitro and in vivo and this could consequently lead to cell death.