P. mossambicus is native to Southern Africa (Angola, Botswana, Eswatini, Malawi, Mozambique, Namibia, eastern South Africa, Zambia, Zimbabwe),[4] but may also be found in Central African Republic, Democratic Republic of the Congo, Gabon, Kenya, South Sudan, Tanzania, and Uganda, and as far north as southern Chad.

[4] This snake grows to 100 to 180 cm (roughly 3-5 feet) in length, and lives in somewhat moist places near a source of water.

It is olive-brown in color, with dark-edged scales and a lighter-hued underside.

It is often confused with the black mamba, as it can raise its head in a similar fashion to the mambas, cobras and other elapid snakes; however, unlike the aforementioned species, the olive grass snake is opisthoglyphous (rear-fanged), with small teeth located at the back of the mouth that deliver mild venom (and/or toxic salival compounds), primarily used for subduing small, slippery or "squirmy" prey such as frogs, lizards and some rodents.

No deaths have been recorded, though possible side effects of envenomation may include localised pain and swelling, nausea and fatigue.