The Swindon-based building society, which has around 650 branches, has committed to not leave any town or city in which it is currently based without a branch for at least two years.
Its announcement came as Barclays announced another tranche of closures – including its branch in Malmesbury.
Nationwide said banks act as a bellweather for the health of a high street, and can be a catalyst for growth or decline.
“Healthy high streets are vital in keeping local communities alive," said Nationwide chief executive Joe Garner.
"They are a major part of our history and identity – a space where we come together. But in many cases they have become almost uniquely transactional, despite consumer behaviour highlighting that people increasingly want to relax and enjoy themselves when out shopping.
"We need to rediscover the sense of belonging that has served communities for centuries and as businesses we need to open our doors to people and not just customers.
"It’s not good enough that we succumb to the perceived inevitable and watch our local shopping centres fade away. We owe it to our communities to make ourselves relevant again.”
The lender is committed to spending £350 million over five years - £80 million this year alone - to ensure its branches remain relevant to the needs of people – from introducing high-definition video and iPads to creating areas where members can chat, read a newspaper or have a coffee.
For the mutual, branch usage remains stable, while there has been significant growth in some areas, with in-branch current account openings increasing by more than a third (38 percent) in the last five years.
On Friday, Barclays announced that its Malmesbury branch would close on June 28, citing declining transactions as a reason for the move.
They said 84 percent of customers registered at the branch do their banking via phone and online. Only 110 customers, they said, use the branch exclusively for their banking.