The hospital was founded in the early 1950’s, next to the Benedictine Mission of Mnero. The mission itself was built in 1914, and was one of the earliest places of Benedictine missionary activities in (the former) Southern Tanganyika.
The first Medical Director of Mnero Hospital, Dr. Leader Stirling, led the construction of the hospital. Thereafter, Dr. Stirling worked for 14 years in the hospital, and later became the Minister of Health of Tanzania from 1976-1980. Throughout these years, the hospital was first run by the Benedictine missionaries, and later by the Salvatorian Sisters and several European doctors. In 1979, the hospital was handed over to the Catholic Diocese of Lindi. After some difficult years, without a doctor in Mnero, the German Development Service (DED) started to provide help in 1989 and has sent several doctors to Mnero Diocesan Hospital. However, this collaboration ended in 2008, leaving the hospital without a European doctor, and for years the hospital was run by only one Assistant Medical Officer (AMO).
The former German doctors who worked in Mnero decided they wanted to keep providing help to Mnero Diocesan Hospital, but also in general improving water supply and education in the village. They founded Solidarität Mnero (SolMne). SolMne supports the hospital in both financial and management matters and in 2016, SolMne send two Dutch doctors to provide both medical, and management support to the hospital.