Timmer is from the Frisian village of Warga (West Frisian: Wergea), where she was exposed to music and songwriting as a child. Together with Johan van der Veen she performed in a talent show under the name Twarres. This led to the duo's success, and in 2000 they scored a hit in the Netherlands and Flanders with the song "Wêr Bisto" recorded in their native West Frisian. They followed this success with the singles "She Couldn't Laugh", "Children," and "I Need To Know." Their debut album, Stream went platinum.
In 2003 Timmer wrote music for the West Frisian-language musical De lêste brief. Timmer and van der Veen decided later that year to break up Twarres. "Face To Face," her first single under the name Mir appeared in 2006. She later released the solo album Files From London.
- "Mirjam Timmer besluit reeks optredens in Estrado". de Stentor (in Dutch). 29 NOVEMBER 2006. Retrieved 14 August 2012.