Construction services group Carillion has inked a deal to provide facilities management services for Nationwide.
The contract is expected to be worth approximately £350m and has the potential to be extended for a further three years, the firm said.
Shares in the company were up 3.5 per cent in afternoon trading.
Under the new contract, which commences on 1 October 2016, Carillion will provide a wide range of hard and soft facilities management and workplace services for Nationwide's headquarters in Swindon, its 15 corporate offices, critical data centres and 700 retail branches throughout the UK.
Carillion's remit will include energy management, risk assurance, asset maintenance, capital works, front-of-house, security, grounds maintenance, mailroom management, porterage and cleaning.
Carillion chief executive Richard Howson said the contract "demonstrates the success of our long-term partnership with Nationwide and our focus on differentiating Carillion by working collaboratively with customers to deliver an outstanding customer experience, using our expertise in whole-life property management and services".
"Our strong emphasis on delivering sustainable services is also a key differentiator, as both Nationwide and Carillion are focused on responsible business practice that maximises the benefits our operations can have on the communities in which we operate," he added.
Carillion has made a series of big contract wins over recent months. In September, the group's stock was boosted after it unveiled a £90m deal with British Gas owner Centrica, and in July the firm revealed two new contracts in Northern Ireland worth up to £600m.