Cumberland, whose head office is in Carlisle, has 34 branch offices and 12 estate agency offices.
This new partnership brings to 20 the number of building societies tied to Norwich Union.
John Leveson, deputy chief executive of Cumberland, said: "This is a great opportunity for us to work with Norwich Union and drive forward our business in what is a rapidly changing market place.
Douglas Ballantyne, director of Norwich Union, said: "We are delighted to welcome Cumberland Building Society to Norwich Union Life and look forward to working with them to develop their financial services business."
