The deal is seen as a coup for the FE sector. The three are City College Manchester, the College of West Anglia, and Plymouth College of Further Education.
They become the main providers of generic training to the Government agency's 73,000 staff, carving up between them most of England, Wales and Scotland.
The colleges will provide short courses mainly in management and information technology.
Training specific to Benefits Agency work will continue to be carried out by the agency itself.
Plymouth College and City College already had contracts to train agency staff in their areas. But the new contracts represent a big expansion.
City College will now cover the whole of the North West as well as Scotland and the West Midlands.
Plymouth College expands its training for the agency four-fold, now covering Wales, the West Country, and much of the South.
It is the first contract with the Benefits Agency for the College of West Anglia, which will train staff throughout most of the East.
A fourth contract for Yorkshire and Tyne Tees was awarded to the agency's own in-house team. The contracts run for three years and may be extended to five.
Angela Chadda, Benefits Agency spokeswoman, said the tendering out to the FE sector was part of the agency's drive for better customer service. "We hope this is the way forward," she said.
Nina Taylor of City College said: "This is a continuation of our relationship with them, but it does mean that we're expanding the work we do. Going into Scotland is a new area for the college.
She said: "It's a good relationship between one of the largest government departments and the FE sector."
Bob Withers, business services manager of the College of West Anglia, said: "We are very pleased. All colleges are interested in non-Further Education Funding Council income. It's a diversification from being entirely fed from the public purse to gaining income from other sources."
Euan Hunter, head of business development at Plymouth College said: "We have been given a contract for more than four times the area that we previously had.
"It's a big step and one which we have achieved because of the quality of service we have given for the past five years."
John Brennan, director of development for the Association of Colleges, called the contracts "a considerable feather in the cap of these three colleges". He said: "This shows colleges are able to compete to provide training to the highest standards."