WNS Assistance now provides an accident management programme, uninsured loss recovery and third-party claims handling for BT's 45,000-strong fleet.
As part of the deal, BT will have access to WNS Assistance's online claims monitoring service. It is also introducing a new downtime management software system.
Janet Entwistle, general manager of BT Fleet, said: 'We are looking to have a relationship with WNS built on trust, teamwork and support. We aim to constantly improve our motor risk management record and deliver the best possible to our customers.'