President Olusegun Obasanjo has agreed to re-open Nigeria's border with Benin after talks with his Benin counterpart, Mathieu Kerekou.
Nigeria said it wanted to stop smuggling and human trafficking
A spokeswoman for Mr Obasanjo said the border was re-opened at 0500 GMT Friday.
The Nigerian authorities sealed off the 773kilometre border between the two countries on Sunday because of alleged criminal activity across the frontier.
The closure has hit Benin's economy, pushing up the price of fuel and other imports.
The two leaders met Thursday in the Nigerian border town of
Badagry to discuss the crisis, which had threatened to damage relations
between the countries.
Benin's leader admitted there were problems.
"There are too many criminals operating in Nigeria who reside in
Benin," he said before the talks.
"I know there are many robberies and attacks near the border."
The main border crossing into Benin is not far from Nigeria's commercial capital, Lagos, and it normally seethes with travellers and traders from Benin, Togo, Ghana and beyond.
Despite a recent price increase, petrol in Nigeria at around 25 US cents a litre is still the cheapest in the region.
Large quantities are smuggled over the border into Benin, and the Nigerian Government has vowed to crack down on this black market saying it costs them a fortune.
Nigeria has also recently banned imports of a number of goods including sugar and exercise books.
Many Nigerian traders were going to Benin to purchase these goods.
The border closure went against West Africa-wide agreements guaranteeing free movement of goods and people within the region.