The government's new rate of £7.20 an hour for over-25s comes into force on 1 April.
But Welcome Break said the national living wage will be the minimum starting rate for all of the company's 5,000 employees across its 27 sites.
Around 2,000 employees (42% of the workforce) are under the age of 25 and Welcome Break said the decision to pay all its staff the national living wage was part of its strategy to attract the best people to work for the company.
Welcome Break said the move, from April, will cost £4m and some employees will receive an increase of 33% on their current wage.
It is the first of the UK's major motorway service operators to make this commitment.
Welcome Break chief executive Rod McKie said: "We are dedicated to offering dependable jobs to the very best people available, and pride ourselves on ensuring Welcome Break is a great place to work.
"If you want to attract the best people you need to reward them accordingly, and as such we've made the decision to give all of our employees, regardless of age, the national living wage.
"This is alongside the excellent career development opportunities with our world-class brand partners and a host of other benefits all our employees receive."
All staff at service stations including South Mimms, Michaelwood, Corley and Membury will be paid the new hourly rate.