Livability and Prospects will merge together to improve their work with people who have disabilities.
It's thought that between them the charities have a staff base of over 2,000 people and more than 1,500 volunteers.
Both charities act as providers of disability services, partnering with both churches and other local agencies to help care for and include disabled people in England, Wales and Northern Ireland.
The two should be fully integrated within the next two years.
Mat Ray, from Livability, told Premier: "We're both Christian charities that are passionate about disability, we've both been working with churches and hands-on with disabled people for many many years, so it just started to make more sense to work together.
"So many times a society says unless you look a certain way, talk a certain way, you're not that valuable.
"But we believe that God's love means that no matter who you are, your abilities are not important, because God loves us all equally."
Archbishop of Canterbury Most Revd Justin Welby, who is also Livability's President, said: "I am delighted to see Prospects joining the Livability family to share their resources, experience and passion.
"Both charities do extraordinary work, empowering those with disabilities to play a full part in the body of Christ and to bless the church and wider community with their gifts.
"I look forward expectantly to see what new possibilities emerge from this exciting partnership.
"Please join me in prayerfully supporting this next chapter in the journey."
Listen to Premier's Hannah Tooley speak to Mat Ray here:
