The Flames assigned Giordano to their American Hockey League (AHL) affiliate, the Lowell Lock Monsters, for the 2004–05 season where he scored 6 goals and added 10 assists in 66 games. He remained in the AHL for much of the 2005–06 season, transferring to Calgary's new affiliate, the Omaha Ak-Sar-Ben Knights. Giordano led the Knights in scoring, recording 16 goals and 58 points in 73 games. Additionally, he was second among defencemen in the AHL in goal scoring and fourth in points. The Flames recalled him to Calgary at mid-season, and he made his NHL debut on January 30, 2006, against the St. Louis Blues. Giordano appeared in seven games with the Flames, and recorded his first NHL point with an assist on April 8, 2006, against the Vancouver Canucks. In the 2006–07 season, Giordano played only five games in Omaha as he spent the majority of the campaign in Calgary. In 48 games with the Flames, he recorded 7 goals and 15 points. Giordano scored his first two NHL goals on October 14, 2006, against the Toronto Maple Leafs.