High-street chain Costa has committed to sourcing all its coffee from Rainforest Alliance certified farms by 2010.
The company, which opened its first store in Russia last month and 1,000 outlet, serves 108 million cups of coffee a year.
From September of this year at least 30% of the coffee used in Costa's coffee drinks, will come from certified sources, equal to about 1,000 tonnes of green coffee over the course of a year.
David Hutchinson, marketing director at Costa, said: "We know it will take time to convert our supply base to certified sustainable sources but we believe it's an investment that is right for our business and the coffee industry as a whole."
In 2006 the company founded the Costa Foundation to support coffee growing communities. Last year the foundation raised more than £300,000, which was invested in building schools, providing teacher housing and reaching materials in Columbia, Ethiopia and Uganda.