St Juste started his career under the guidance of Simon Clifford at Garforth Town. He became a graduate of the LeedsBrazilian Soccer School's program and was spotted by Football League Two side Darlington, joining them early in the 2004–05 season. He made his Darlington debut in November 2004, playing as a substitute for Adrian Webster in the 2–0 win away to Cheltenham Town. He made his second appearance for Darlington on 3 January 2005 as he played the full 90 minutes and helped the team to a 3–1 win over Macclesfield Town. On 19 March 2005 St Juste made his seventh appearance for Darlington in an away match against Grimsby Town, scoring his first goal for the club. St Juste hit headlines by scooping a hat-trick of awards. He walked away with the young player of the season and both goal of the season awards for his goals against Grimsby Town and Bristol Rovers. He was out of contract at the end of the 2004–05 season and was linked with Southampton who initially insisted that they did not want to sign him. However, he eventually signed for Southampton on a short-term contract in September 2005 following Simon Clifford's appointment as a coach at the club. He failed to appear for Southampton and rejoined Garforth Town in November 2006. He left Garforth to join Sandnes Ulf in 2009. In February 2011 St Juste signed on loan for non-league 'phoenix club' Chester F.C. until the end of the season but his loan was cancelled at the end of March after he failed to make an impact whilst on loan. He later joined F.C. Halifax Town in September 2011. Despite coming on from the bench in most games, Jason was able to score in two games for the Shaymen, at home to Blyth Spartans and away at Corby Town. In the 2012–13 season, St Juste started more games due to a groin injury to Scott McManus, but this meant playing in an unfamiliar left back position. St Juste had a very strong start to the season, including a goal against Chelmsford City in the FA Trophy Third Round, but a hernia meant that he would spend a month on the sidelines. He joined Bradford Park Avenue A.F.C. on 5 September 2015. In summer 2016 he joined Boston United. In summer 2017, he joined FC United of Manchester. In September 2017 he moved to Trafford on dual registration terms.
