The deal covers wide and local area network services, remote access, voice and telephony, as well as compliance management and security – for all of the company's global locations.
The American firm, which employs approximately 28,000 people globally, has its UK headquarters in Uxbridge, Middlesex. Its key pharmaceutical products are based around cancer, HIV/AIDS, cardiovascular disease, diabetes, hepatitis and arthritis.
Bristol-Myers Squibb aims to create a more standardised network infrastructure as part of the deal, as well as to improve collaboration between staff. The company will be able to meet the "stringent compliance requirements" of the pharmaceutical industry, BT said.
Rick Yborra, vice president of network and hosting at Bristol-Myers Squibb, added that it was important that BT had the "ability to flex" with the pharmaceutical firm's changes over time.
When the initial deal was signed in 2005, BT hailed it as major expansion for its global services business outside the US.
Two of its largest other deals include a global networking contract with Thomson Reuters, and a patient records deal in the UK with the officially 'cancelled' NHS National Programme for IT. Severe problems on some stages of both of those deals are understood to have contributed to BT Global Services profit warnings in recent years.