AU commission chair Nkosazana Dlamini-Zuma said the threat posed by the Islamist group required a “collective, effective and decisive response”.
Boko Haram has seized control of a swathe of north-east Nigeria and killed thousands in a six-year insurgency.
Four of Nigeria’s neighbours – Benin, Cameroon, Chad and Niger – have agreed to contribute troops to the task force.
Speaking after AU talks in the Ethiopian capital, Addis Ababa, Ms Dlamini-Zuma said the Multinational Joint Task Force (MJTF) would have an initial mandate of one year.
She said it would conduct “military operations to prevent the expansion of Boko Haram and other terrorist groups’ ACTIVITIES and eliminate their presence”.
The PLAN is now expected to be submitted to the UN Security Council for approval.