Jason Shackell is a tall left-footed centre-back from Stevenage who progressed through three years of Norwich's academy.

He signed a two year professional contract towards the end of January 2003. He became the first home-grown player to sign a long-term deal for five years. For though Aylsham's Lewis Blois was handed a one-year professional contract to prove his worth, Darel Russell was the last Colney product to sign for longer - way back in November, 1997.The hope is that the security of a two-year contract will allow Shackell to blossom into a regular member of Worthington's first-team squad. "The boy deserves the two years," said Worthington. "It takes the pressure off him. Rather than just having the 12 months, he's got 24 months to go and produce." Size, maturity and a good left foot are three good reasons why the teenager can now look forward to a professional career at Carrow Road. "He's a good size for a centre-half," said Worthington, with Shackell standing a good 6ft 2in tall. "Plus he's matured over the last 12 to 18 months, both as a player and as a young man. He's joined with the professionals in training and held his own very well and I wouldn't have any problem with putting him in if the situation arose."

Jason became the third Academy player, after Ian Henderson and Dean Sinclair, to make his first team debut during 2002/03 when he played against Derby in a 2-1 defeat on March 5th 2003 replacing Adam Drury at the last minute when Drury succumbed to a virus.

Shackell was appointed the club's captain for the 2007/8 campaign and signed a new contract in October 2007 keeping him at Carrow Road until 2010. He lost the captaincy to Mark Fotheringham after Glenn Roeder was appointed manager

In July 2008, he was the subject of a £1m bid from Wolves but this was rejected by Glenn Roeder as the Canaries only had 4 recognised defenders in their squad at the time of the enquiry.

On 1st September 2008, Jason finally moved to Wolves, signing a four year contract for a fee rumoured to be between £750,000 and £1million.

Shackell made a surprise return to Norwich on 10th February 2009 sgning on loan until the end of the season. he had played just 13 games for Wolves. He made his second debut for Norwich in the 1-0 defeat at Preston on 14th February 2009. He made 14 appearances for City whilst onloan but could not help City avoid relegatito League One following their 4-2 defeat to Charlton on 3rd May 2009

Shackell was loaned out again on 14th August 2009, joining Doncaster Rovers on an initial month-long loan. This was extended initially until the end of December 2009 and then aagin until the end of the 2009-10 season.

In mid-May 2010, Jason signed for Mark Robins' Barnsley, and became captain

At the end of the 2010/11 season, Shackell was linked with Burnley, Derby (who had two failed bids) and Portsmouth (who were due for talks over a £1million move). Jason eventually signed for Derby on 21st June 2011 on a three year contract for a fee believed to be in the excess of £1m

In May 2012, he was the subject of a £1.2million bid from Burnley which Derby rejected. It was eventually accepted on 5th July 2012 for an undisclosed fee which the BBC thought was £1.1million. Derby had turned down 4 bids for Shackell. Shackell signed a four year contract with Burnley. Shackell said "I knew Derby were quite keen to get some money in so I thought it could be a possibility. I had a great year there last year and I got on really well with the lads. It's a fantastic club and I really did enjoy my time. But if the club wanted to cash in, as they say, it left me in a difficult position. I'm not going to hang about somewhere where you're not sure where you stand. Once I met the gaffer (Eddie Howe) and his team, I was very impressed and I was really looking forward to coming down. "

Shackell and Burnley won promotion to the Premier League on April 21 2014 when they beat Wigan 2-0. They were relegated at the end of the following season.

On 23rd July 2015, Jason rejoined Derby

On 25th January 2018, Shackell was loaned to Millwall until the end of the 2017/18 season. He has six months left on his deal with the Rams and could join Millwall permanently when it expires. he has been out-of-favour since Gary Rowett took over as manager in March 2017. He has made just two appearances in 2017/18 for his parent club, both in the EFL Cup. Shackell made 9 appearances for Millwall - seven of which were as substitute.

Shackell was released by Derby at the end of the 2017/18 season. He had played 62 games for Derby.

Shackell joined Lincoln City on Transfer Deadline Day (9th August 2018), signing a one year contract.

On 13th April 2019, Lincoln secured promotion to League One and claimed the League Title on 22nd April 2019 drawing 0-0 with Tranmere. He was named in the Professional Footballer's Association League Two team of the year along with teammates Harry Toffolo, Neal Eardley and John Akinde. Shackell then signed a one year contract extension. He had made 40 appearances in 2018/19, scoring five goals.

On 29th May 2020 it was reported that Shackell was one of 11 players to be released by Lincoln. In total, Shackell played in 69 games for Lincoln, scoring seven goals.