The Catholic Diocese of Ngong (CDoN) was established in 1959 as a prefecture and it attained Diocesan status in 1976. 

The Diocese is situated in the Southern part of Kenya, and operates mainly in the Counties of Kajiado and Narok. The CDoN covers an approximate area of 39,619km², with a population of 350,000 people. It comprises thirty -seven (37) parishes clustered into four (5) deaneries viz. Kilgoris, Narok, Ngong, Kajiado and Loitokitok.

The Diocese runs a number of development and pastoral programs in collaboration with various actors who include: beneficiaries/faithful, peer institutions, other churches, the Government of Kenya (GoK) as well as various development (funding) partners. 

The Diocese has an established secretariat headed by both clergy and lay professionals. The Moderator, who reports directly to the Bishop, oversees the effective and smooth administration of all the units within the Diocese. Each department has an oversight council/committee comprising selected lay professionals and clergy who meet regularly to oversee their respective units’ activities.

Bishop Emeritus Collin Davis was the first Bishop of the Catholic Diocese of Ngong. He was succeeded by Bishop Cornelius Schilder (2003–2009). Thereafter, the Diocese was under the administration of His Eminence John Cardinal Njue, the Arch-Bishop of Nairobi, until April 2012, when Rt. Rev. John Oballa Owaa was consecrated as the substantive Bishop of the Diocese.