Giroud spent five years developing in Grenoble's youth academy before signing his first professional contract at the age of 21. He later admitted that signing his first contract was an important part in his development as a player, stating "It took me signing my first professional contract to become aware of my abilities. If you [a club] trusted me, it was because I must have had some qualities. " Ahead of the 2005–06 season, he was promoted to the club's reserve team, which was playing in the Championnat de France amateur 2, the fifth level of French football. Giroud quickly became an important player in the team scoring 15 goals in 15 matches. His performances over seven months with the reserve team resulted in the player being called up to the senior team in March 2006 by manager Thierry Goudet. Giroud made his professional debut on 27 March appearing as a late-match substitute in a 1–1 draw with Gueugnon in Ligue 2. He remained a part of the senior team for the rest of the campaign making five more substitute appearances.