Fenger was born in Kongens Lyngby, and began her musical career in 1980 with the band Sweet Intentions, which was led by the vocalist Nanna.

She participated in the 1982 Danish Melodi Grand Prix as a choir singer on the song "Marie", which was performed by Jørgen Klubien and Carsten Elmer.

[12] In collaboration with the jazz musician Chris Minh Doky, Fenger produced Vuggeviser in 2007, which contained new interpretations of classic lullabies such as "Den lille Ole med Paraplyen" and "Mester Jakob".

[15] Alongside her own career, Søs Fenger has appeared on a number of other artists' works, including: Mek Pek, Gnags, Henning Stærk, and Anne Linnet.

In 1987, Søs collaborated with the band Moonjam to release "Ticket to Peace," a single which protested against nuclear weapons testing in Nevada.

That same year, she contributed to the single "Du si'r, dit hjerte er hårdt som sten" in support of the youth crime prevention fund in Denmark.

[17] In support of the Dansk Refugee Council's collection for children in Sarajevo, Fenger contributed to the song "Gi' dem et håb" in 1995.