Former Norwich scout Tony Nash reported in an interview with the Peterborough Telegraph in February 2012 that he had spotted Julian Joachim and got him into Noriwch for a trial only for him to be rejected by the Canaries.

Instead he came through the youth system at Leicester City, and went on to score the club's first ever Premier League goal on the opening day of the 1994-95 season in a 3-1 home defeat to Newcastle United. He was sold to Aston Villa in 1996 for £1.5 million, making his debut for them as a substitute against Wimbledon on 24 February 1996. After five seasons in the Premiership, Joachim dropped down a division to play for the relegated Coventry City in a deal that saw Villa exchange Joachim plus £2 million for Mustapha Hadji

In 2004 Joachim moved to Leeds United, a club heavily in debt and in the process of rebuilding an inexpensive team, on a free transfer. He made 10 starts and 17 substitute appearances in the league for Leeds that year, but could only deliver two goals before being loaned out to Walsall for the final two months of the season. After turning down Walsall he dropped down another division to League Two. Joachim spent the 2005–06 season with Boston United whom he joined in July 2005. He moved to another League Two side, Darlington, for a club record fee of £100,000 on 14 August 2006. Despite making 40 league appearances and scoring 9 goals as Darlington reached the play-offs, Joachim was released at the end of the 2007–08 season. He subsequently moved into non-league football, signing with newly-promoted Conference North side King's Lynn in June 2008

Budget cuts following King's Lynns's demotion to the Northern Premier League Premier Division in May 2009, resulted in Julian not being offered fresh terms for the 2009-2010 season. He briefly played as an amateur in The Leicestershire Senior League For Thurmaston Town at the start of the 2009-10 season, but a couple of weeks later he signed semi professional terms with non league club Quorn. Joachim has signed on for United Counties Premier Division side, Holbeach United for the 2010/11 season. On 14 July 2011 Joachim re-signed for Boston United on non-contract basis. On 26 August 2011 after only making one league appearance Joachim was released after failing to impress in his second spell with The Pilgirms. He then joined Coalville Town.

In August 2013 Joachim, aged 38, came out of retirement and re-signed with United Counties Premier Division side Holbeach United for the 2013–14 season. On 29th November 2013, he signed for United Counties Division One side Oadby Town.

Joachim starred in the England National Under-18 side that won the European U-18 Championships in 1993. He also had nine England Under-21 caps to his name before he was called up by St. Vincent and the Grenadines to represent them at senior level. However, due to him playing for England at U21 level he was ineligible to play for the Caribbean team, only being informed of this upon arrival in St. Vincent for a World Cup qualifier in April 2000. He was also part of England's U20 squad that finished third at the 1993 FIFA World Youth Championship in Australia.