The organisation will pay all its employees, including contractors and temporary workers, the living wage, which is set at £8.80 in London and £7.65 for the rest of the UK.
The building society will also become a principal partner to encourage other organisations to sign up.
Alison Robb, group director at Nationwide, said: “We are hugely proud to become a principal partner of the Living Wage Foundation, and we are looking forward to working with the foundation to encourage other employers to sign up in future.
“Nationwide’s living wage accreditation shows our commitment to doing the right thing by our employees and we are proud to take a leading role in the campaign for fairer pay.”
Rhys Moore, director of the Living Wage Foundation, added: “We are delighted to welcome Nationwide to the living wage movement as both a principal partner of the Living Wage Foundation and an accredited employer.
“As the UK’s largest building society, this brings the living wage to high streets across the country, and showcases that the best employers are voluntarily signing up to pay the living wage now.”