The Danish International defender played a key role in the Great Escape and has pledged his future at The Hawthorns until 2008.
The player of the season in 2004 has proved a real fans favourite with supporters dedicating an away game at Reading in his honour by dressing up as vikings.
Gaardsoe said:"There was no doubt in my mind when we were negotiating the deal that I wanted to stay.
"I had a bit of interest from other clubs in this country and abroad but I'm very happy here."
"I'm proud to play in front of these fans. They've been really good to me ever since I came to the club.
"And I'm really happy with the with the management team plus the atmosphere and spirit at the club.
"I think we've got some great years ahead of us."