Anyone who leaves more than a few spoonfuls on their plate from the all-you-can-eat buffet is fined £2.50, which goes straight to the Oxfam shop across the road.
Toks Odebunmi, owner of Suya Express in Dalston, said he was fed up with people piling up their plates with pounded yam and jollof rice, then wasting half of it.
He put notices on the tables informing customers of his new policy, he said, and most of them had welcomed the idea.
"I've accosted people already and it has worked," added Odebunmi. "The policy is to deter people from wasting food.
"There are lots of people in Africa who don't have the opportunity to see this amount of food, let alone to buy it."
He said Oxfam deserved the money because they did a lot of work in Africa.
Hayley Baker of Oxfam said:"What a fantastic idea - it makes the restaurant customers give some thought to extreme poverty in Africa. Brilliant."