She is the winner of the third series of The Voice Australia.
Nissen competed in the Dansk Melodi Grand Prix 2016 on February 13, 2016, performing the song "Never Alone", which was written by Danish Eurovision winner Emmelie De Forest, producer Rune Westberg, and MoZella. Anja Nissen came in second place with 36% of the vote.
In 2017, it was revealed that she would compete in the Dansk Melodi Grand Prix 2017 for a second time with the song, "Where I Am". She went on to win, and represented Denmark in the Eurovision Song Contest 2017, where she achieved a 20th place.