Coach tickets are to be sold at more than 11,000 Post Office branches nationwide.
Tickets are being made available to around 1,000 destinations served by National Express.
The link-up will also enable people to purchase coach travel to airport terminals along with travel insurance and foreign currency.
Around a third of all 17 million annual journeys taken with the UK’s largest coach operator are to airports.
National Express UK coach managing director Tom Stables said: “In this day and age, some businesses overlook the importance of face-to-face bookings, but we are all about increasing the options on offer for our customers.
“The Post Office is a fixture of the UK high street and we hope the partnership helps give high streets up and down the UK a welcome boost.”
Post Office head of payments Alan Smith said: “Our work with National Express is a shining example of how we are committed to our customers and enhancing our services within the network, enabling people to arrange their coach travel with unbeatable accessibility and ease.”
“The partnership offers more choice and flexibility to our customers and by walking into any one of thousands of participating Post Office branches, they can now benefit from coach services that can take them all over the UK and beyond.”