Phil, a former soldier who sustained a spinal cord injury while serving in Iraq in 2008, said he felt privileged to take on the role for the disability charity.
The Papworth Trust runs a range of services for disabled people, providing employment, rehabilitation, housing, personal and learning support.
Phil, who raised more than £1 million for injured service personnel by taking part in several grueling sports challenges, said: "It's an honor to become an envoy for Papworth Trust.
"They carry out some tremendous work and I feel privileged to have met some service users and the dedicated staff who are clearly devoted and committed to making a significant difference to others. I look forward to a close relationship with Papworth Trust in the future."
The BBC Sports Personality of the Year award winner will now take part in Papworth Trust fundraising events and help celebrate the achievements of the charity's service users.
As part of the relationship, Papworth Trust chief executive officer Adrian Bagg will also act as an adviser on disability-related issues in the development of Phil's new £15 million youth center.
Named the British Inspiration Trust (BRIT), the center will inspire young people facing adversity between the ages of 16 and 25.
Adrian said: "Phil has achieved so much including the Channel Row, London Marathon and El Capitan Climb.
"His focus now is on supporting disabled people and it's clear that he shares our passion. Working in partnership will help us to achieve even more."
Papworth Trust supports more than 17,000 people from the East of England and beyond through a wide range of services. The trust also works with the Government, employers, service providers and commissioners to promote disability equality and good practice.
For further information visit www.papworth.org.uk.