Excoecaria grahamii Stapf is an Euphorbiaceae used in traditional medicine in Burkina Faso and many other parts of the world. Phytochemical compounds as total phenolics, flavonoids and alkaloids have been measured. Acute and subacute toxicity of the plant have been studied on NMRI female mice. The results showed that the extract contained total polyphenols and flavonoids but not alkaloids. In the acute toxicity the DL50 could be greater than 5000mg/kg bw. The extract had no significant difference on organs weight and biochemical parameters during 72h after single oral administration. During the subacute treatment by oral administration no animal was dead. There was significant difference in body weight at 75mg/kg bw compared to the control mice that received distilled water. There was significant difference in food consumption. According to relative organ weights, water consumption and biochemical parameters, there was no significant difference. Histological study of important organs such as kidney, heart and spleen showed no damage when compared to the control. However, liver and lungs presented signs of damage. Aqueous extract of Excoecaria grahamii has no toxic effect at the organ level in acute toxicity but regarding the subacute effect, the plant has a toxic effect on some organs such as liver and lungs.