The work in Tansen began as a result of the visit of ornithologist Dr Robert Flemming (author of "Birds of Nepal"), his physician wife Dr Bethel Flemming and their family and Dr Carl Friedericks and his family in the winter of 1951 –1952. During their visit to Tansen they examined and treated patients and even performed a bladder stone operation!
The local people invited them to come back and establish a hospital, and by 1954 permission was given for the newly formed United Mission to Nepal to start health work in the Kathmandu valley and Tansen. Dr Carl Friedericks initially opened a clinic in rented accommodation in the bazaar as the work grew land was granted in the Bhusaldanda area just east of the bazaar to build a hospital.
In 1959 the first building was opened, and ever since then the hospital has continued to grow. Recent additions are the Carl and Betty Anne Friederick’s building which houses a training hostel, doctors’ accommodation and classrooms, and a new nursing station in the medical ward which has freed up space for a High Dependency Unit.