"[2] Nilsen is noted for the sincerity of her song writing and the clarity and range of her voice, characterized as "unique" and "beautiful".

Nilsen made her stage debut in 2007, and she was nominated for a Norwegian Grammy in the category of Best Female Artist in December, 2011.

Nilsen has had a career for several years as a voice actress, dubbing character roles into Norwegian for several feature films and television, mostly animation.

[6] At that time she turned to a "secret notebook full of songs that she had been compiling since her early teens" to express herself as an artist.

In awarding Nilsen the prize for best debut artist, the jury described her as having "the courage to write simple, personal and intimate lyrics in Norwegian".

[8] As part of the award, Nilsen received a record contract which produced 2009's Vi som ser i mørket (We Who See in the Dark).

[15] oh, how to make roses grow through a long winter when you live so far north how to feed birds that don’t dare to come near how to believe in love when you know what it’s like oh, such simple things[16] Aftenposten characterized the album's lyrics as "well written and honest".

[14] Nilsen was described by one album reviewer as being "remarkably adept at combining bright colors with subtle hints of darkness," adding, "this usually prevents this light, nimble music from becoming overly cute.

[18] The single, "Alle snakker sant", received praise in the pages of The Guardian[19] and among Norwegian music critics.

[4] On 15 December 2011 it was announced that Siri Nilsen had been nominated for a Spellemannprisen (Norwegian Grammy) in the category of Best Female Artist for her album, Alle snakker sant – with the award ceremony being conducted at the National Theatre in Oslo on 14 January 2012.

"[25] Nilsen is described as having a "strong artistic presence"[11] and a voice which has a "large register", which is "comfortably clear" with a "steady top and powerful down.

"[29][30] When I was younger, I missed being able to hear music from my own time in my own language, so it felt natural for me to start writing my songs in Norwegian.

[34] In June 2012, Siri Nilsen gave birth to a daughter with Norwegian actor and comedian Anders Bye, with whom she has been in a relationship for several years.