Tessa Thiadens was born in Nairobi, Kenya, grew up in Bandung, Indonesia, and lives in Utrecht, Netherlands. 

After a first posting in Bangladesh, she worked for MSF in Walikale town in eastern Congo. There was a huge need for medical care because of armed conflict, continued instability, and a shortage of qualified personnel. Due to the insecurity, few aid agencies working there.

After her time in eastern Congo, she worked as a medical team leader in the village Lankien in South Sudan. She led the medical staff at the hospital, which has grown over the years from a clinic to a hospital with comprehensive care: offering everything from surgery and obstetric care to treatment for malnutrition.