The collaboration between Norfolk County Council and charity Barnardo's will see the creation of a jointly-run looked-after children's service that will start operating later in the year.
Announcing the move today, Education Secretary Nicky Morgan said it is part of the "widest-reaching reforms to children's social care and social work in a generation".
"We must take swift action where services are letting children down," she said. "That is why I'm announcing that Norfolk children's services will begin working with Barnardo's to establish a joint looked-after children service - the first in the country."
Michael Rosen, Norfolk's executive director of Children's Services, said: "This partnership has been several months in the making and supports the particular needs of Norfolk children looked after by the local authority and our care leavers.
"We want to bring new ways of working to Norfolk and plan to combine resources to achieve common aims. Our partnership with Barnardo's does not involve any transfer of staff or funding and each organisation remains independent in terms of policy and governance."
Removing responsibility for children's social care services from struggling councils and handing it to "high performing local authorities, experts and charities", is a key part of the government's children's services reforms unveiled earlier this year.
Last October, Norfolk children's services was rated inadequate for the second time in two years, and in January Dave Hill, president of the Association of Directors of Children's Services, was appointed commissioner at the council to assess whether it should retain control of services.
Barnardo's corporate director of children's services, Sam Monaghan, said: "Working with Norfolk presents an exciting opportunity to explore how we can deliver better outcomes for some of the most vulnerable children and young people in the county.
"This feels like a genuine partnership, bringing the skills of both organisations to look afresh at the experience of children in care and for young people leaving care, improving their life chances and building robust services for the future."
Roger Smith, chairman of Norfolk's children's services committee, added: "I welcome this partnership as I am determined to make sure that Norfolk's services for looked after children and care leavers now improve as rapidly as other areas like safeguarding and support for education - improvements which have already been acknowledged by Ofsted.
"I am keen the council hunts out expertise and good practice wherever it can be found to support rapid improvement for the sake of Norfolk's most vulnerable children.
"It is part of our ambitious plan to move faster towards not merely a 'requires improvement, Ofsted rating, but to becoming a good or outstanding department. That is what Norfolk children deserve."