His international career began in 1994 at the Junior World Championships in Athletics, when he won the silver medal in the 100 -meter run. He had great successes in the following years, especially with the British 4x100 - meter relay. The highlight was the Olympic gold medal along with Darren Campbell, Marlon Devonish and Mark Lewis - Francis at the 2004 Olympic Games in Athens in front of the squadron from the U.S.. He was the first runner of the quartet.
At the World Athletics Championships in Helsinki in 2005, he retired about 100 meters from the semi-final and won with the British sprint relay bronze medal.
His biggest single successes gained Gardener in the hall on the 60 - yard dash: in 2004 he won at the World Indoor Championships in Budapest the gold medal, he also won four in a row ( 2000, 2002, 2005 and 2007), European Indoor champion, having already won 1998 silver had.
In the summer of 2007, Jason Gardener ended his career.
He had a competition weight of 70 kg at a height of 1.78 m.