The 2009 Junior World Championships in Canmore, Canada began in disappointment: Bø finished as number 23 in the individual discipline with a total of five shooting errors.

During the 2009 European Championships in Ufa, Russia, Bø was the most successful biathlete and claimed the gold medal in all four races he entered (individual, sprint, pursuit and relay).

In the 2009–10 season, Bø continued his positive development in the IBU Cup, coming in sixth in the individual discipline and second in the sprint.

Bø was chosen for the Norwegian relay team, which claimed the gold medal before runners-up Austria and bronze-medalists Russia.

[6] At the World Cup stop in Kontiolahti, Finland, Bø ran the last leg for the Norwegian mixed team, securing the win for Norway.

[8][9][10] On 5 January 2007, Bø won his first World Cup event, the sprint race in Hochfilzen, Austria, beating runner-up Serguei Sednev by 27.5 seconds.

[16][17] At the World Cup stops in February in the United States, Bø continued his good form; his worst result was sixth place.

[18] One week later in Fort Kent, Maine, Bø finished all three races in third place (sprint, pursuit and mass start).

[25] Two days later, Bø claimed his second title alongside Ole Einar Bjørndalen, Alexander Os and Emil Hegle Svendsen in the relay,[26] becoming the most successful biathlete at the championships with a total of five medals.