Euell rose through the ranks at the Wimbledon youth academy to establish himself as a first team player in 1997. He spent one season with Wimbledon in the Football League Division One after they were relegated from the FA Premier League in 2000. However in 2001, Charlton Athletic signed him for £4.75 million, bringing him back to the premiership.
Jason has been a role model for many youngsters who share his problem of being deaf. Although he is only deaf in his left ear, he has not let this disability stand in his way, he has been an ambassador for the National Deaf Awareness in Sport Alliance for the past 7 years, attending various functions and fund raising events.
He joined Middlesbrough in August 2006 for £300,000. Upon joining Middlesbrough he declared "I'm over the moon". Euell played his first game in a Boro shirt away at Arsenal on September 9, 2006. The game finished 1-1, with Euell setting up James Morrision to give Middlesbrough a 1-0 lead before Thierry Henry equalized.