The Diocese of Masasi was established in 1926. It occupies an area of 68,000 sq km and covers the Southern Part of the Republic of Tanzania, bordered by Mozambique to the South, the Indian Ocean to the East and the Selous Game Reserve to the North and West. The diocese covers the Mtwara and Lindi regions and the Tunduru district in Ruvuma region.

It has 282 Churches, 24 Evangelists, 48 Catechists and 72,631 Christians. The number of Christians belonging to the Anglican diocese form 2.4% of the area population of 3,268,408.

The diocese is involved in Primary Health Care, dairy cow and goat rearing, water supply and sanitation, health and medical services including dispensaries, fish farming, sustainable seed multiplication, education and training.