The European Parliament has awarded BT two framework contracts for networked IT services worth a total €120 million (£100 million) over five years.
As well as IP telephony, unified communications, videoconferencing, internet access and IT security services, BT will supply network equipment and applications under the contract.
It will also provide related professional services such as systems integration, maintenance and training, to support the European Parliament's telecommunications infrastructure and systems.
BT will deliver the services at the European Parliament's sites in Brussels, Luxembourg and Strasbourg.
The network security aspect of the BT contract will be crucial as the parliament was reportedly the victim of a cyber attack, in March, two days after the European Commission and the European Union's External Action Service also detected a sustained attack on their own systems.
Meanwhile, the contract follows a £10.5 million deal the European Parliament signed in September with Accenture for the development, maintenance and support of applications across its operations.