Jaaskelainen, 33, is now expected to see out his career at the Reebok Stadium in what has become a home from home for the Finland international.
Jaaskelainen has gone on to make the number one spot his own but there were fears he would leave this summer as he was out of contract.
However with Bolton managing to avert relegation he has decided to stay on and continue to work with manager Gary Megson.
Gardner also made his debut in 1998 and the 29-year-old Jamaican has shown his adaptability by playing in midfield as well as defence.
Jamaica captain Gardner was also out of contract this summer but like Jaaskelainen became energised by the way Bolton battled to beat the drop.
He joined the club two years after impressing in the 1996 World Cup finals in France.