The 23-year-old - sister of UEFA Women's Champions League winner and Olympique Lyonnais striker Ada Hegerberg - began her career in the youth teams of Sunndal and Kolbotn, who gave her her first professional contract at the age of 16.
She spent three years with the latter, where she finished third in the Toppserien in 2010 and 2011. Ahead of the 2012 season, she and Ada signed for Stabæk, where she finished second in the league and won the Norwegian Cup. In the January of 2013, she then signed for German club 1. FFC Turbine Potsdam, but only made four appearances in the following season. Hegerberg subsequently joined Damallsvenskan side Göteborg FC.
The midfielder has played for many Norwegian youth teams, including the 2011 UEFA Women's U-19 Championship and 2012 FIFA U-20 Women's World Cup, where she managed a goal. She made her senior international debut in a friendly against Sweden.
Speaking to the club's official website, City manager David Parker said that Hegerberg is a "wonderful" addition to the league, and truly believes she has the potential to be "one of the best players in Europe."
He also believes she adds a "different dynamic" to his group and gives the Blues a "greater attacking threat from midfield". Parker insisted that Hegerberg will be a fan favourite due to her "ability and personality on the pitch".
The ex-Potsdam player was delighted to join the Midlands club too and believes it to be "one of the big clubs in British women’s football". She said that it was time to leave Gothenberg after three years and that, once the deal was on the table, "couldn't wait to get stuck in with Birmingham City."
Hegerberg insisted that the transfer was "attractive" after learning the club's idea of moving forward. She also believes she could have "a lot to contribute to the team's future development."