At the 2009 World Youth Championships, Pedersen became the world champion in the 100 metres hurdles (76.2 cm) in a time of 13.23. In the semifinals, she ran a 13.20 which was a European record for U18 class until 2011. At the 2010 World Junior Championships, Pedersen won the 100 meters hurdles in a time of 13.30 and in the process set a new Norwegian junior record. She was awarded the Karoline Price the same year.