Another Welsh product from the youth team (see also Craig Bellamy, Deryn Brace, Tom Ramasut ), Chris broke into the Norwich first team in 1997/98 and made a total of 16 appearances scoring 3 times. He played in an attacking midfield role predominantly on the left, stepping into the vacancy left by Darren Eadie. During 1997/98, he gained Welsh B honours and the interest of Premiership side Newcastle. He later won full international honours making his Welsh debut against Malta in 1998, followed up by a game against Tunisia.

Chris was linked in December 2000 with a move to Bobby Gould's Cardiff which was investing heavily in young Welsh talent with the signing of Arsenal's young Welsh international Rhys Weston and West Brom's Daniel Gabbidon. In April 2001, Chris' run of good form led Premiership scouts from Leicester and Aston Villa to watch him. However Villa scout Mark Lillis felt that, after seeing Chris' performance in the 1-1 draw with Sheffield United, that Chris couldn't add anything extra to the Villa squad. Despite his poor form in Norwich's opening match at Millwall (lost 4-0), Chris was called up to the Welsh Under 21 squad for their games with Armenia and Norway at the beginning of September 2001. Lost his place in Norwich's first team through injury and the form of Paul McVeigh and Clint Easton and did not start a first team game after Boxing Day 2001. Had a strong 2002 pre-season and was called up for the full Welsh squad for the trip to Croatia on 21st August 2002

Making just three appearances for the Canaries in 2002/03, Nigel Worthington allowed Chris to join Bristol Rovers on a month's loan on 21st February 2003. Worthington stated that this was to give Chris a chance to get games under his belt. He immediately made an impact, scoring Rovers' goal in a 1-1 draw with Macclesfield the following day. Llewellyn's stay in Bristol was extended until the end of the 2002/03 season althougn Nigel Worthington was quick to emphasise that Llewellyn was coming back to Carrow Road in the summer.

This in fact was untrue as Norwich announced on April 8th 2003 that Chris, and defender Paul Heckingbottom, were to be given free transfers. Rovers have suggested that they would be very keen to extend Chris' stay in Bristol. After Chris returned to Norfolk when his loan at Rovers expired, Swansea manager Brian Flynn announced in May 2003 that Chris was at the top of his shopping list. Chris was keen to return to his hometown and commented that Flynn "sold the club to me and I was very impressed with his ambitions". However Swansea's ambition might be dented by the fact that First Division Bradford have also expressed an interest. Another club to express interest are Third Division Leyton Orient.

Norwich came to an agreement with Chris in early June 2003 to cancel his contract, and pay him off some of his wages. This cleared a high wage earning member of squad from the wage bill whilst giving Chris a fresh start. QPR were then linked with a move to bring Chris to Loftus Road. On 30th June 2003, reports from North Wales suggested that Chris and namesake Chris Armstrong (ex-Spurs) were on Wrexham's shopping list as a new forward line for the Dragons. The next club to declare an interest in Chris' services were Notts County on July 1st 2003.

Despite an approach from an unnamed Scottish Premier League side, Chris opted to join Wrexham, signing a two year deal on July 2nd 2003. A strong 2003/4 season saw him recalled to the Welsh squad in May 2004 for the friendlies with Norway and Canada. Coming on as an 85th minute substitute for Craig Bellamy against Norway on 27th May 2004 won Chris his third international cap, five years after his second. Wales' 0-0 draw with Norway saw Norwegian manager Aage Hareide's 100% record broken.

Chris moved to Hartlepool on July 4th 2005, one of three players to leave the Welsh club that day. He made 24 appearances in his first season with Hartlepool and retured to Wrexham on 29th June 2006 on a two year contract, having had his contract with Hartlepool ripped up by mutual consent. "It's good to be back," Llewellyn told the club website

After scoring 10 goals by January 2007, Llewellyn was a target for his former Wrexham teammate Darren Ferguson, son of Sir Alex, who took over at Peterborough.

A poorer return in 2007/8 where Llewellyn scored just twice played a factor in Wrexham's relegation out of the Football League and into the Conference. Following relegation, Wrexham decided to reduce their wage bill and released seven players on 6th May including Llewellyn who has been linked with Peterborough, newly promoted to League One.

On 30th June 2008, the Non League Paper website reported that Llewellyn was in talks with Welsh Premier side Rhyl who had signed his former Wrexham colleague Neil Roberts. Instead, he signed for Grimsby Town on 3rd July 2008 becoming Alan Buckley's fourth summer signing. Llewellyn, who signed a two year deal, is seen as a direct replacement for Ciaron Toner who has left the Mariners.

Llewellyn left struggling Grimsby at the end of the 2008/9 season and returned to Wales to sign for Neath. Llewellyn scored on his Welsh Premier debut against Connah's Quay and went on to notch nine goals last season from thirty-four appearances in an Eagles' shirt. Neath manager Andrew Dyer praised Llewellyn's performances and described him as "the best striker in the league". However on 9th June 2010, Chris switched to Llanelli "by mutual consent" and signed a two-year deal at Stebonheath Park

He joined Aberystwyth Town on loan in January 2012. He also runs Soccer Skills Swansea.

In the summer of 2012, Chris joined Welsh Football League Division One club West End, who are based in Swansea. The 32 year old will combine the position of assistant manager with that of playing.

He then took up a part-time role at Swansea's academy coaching their Under-14s, which then became a full-time position in October 2012. He was later promoted to look after Swansea's Under-18s and then the Under-21s with whom he won the Professional Development League in 2014/15 and a place in the FA Premier Youth League. However at the beginning of July 2015, he was moved to manage Swansea's Under-15s with the Academy's Head of Coaching Dave Adams taking charge of the Under-21s. He was then moved to manage the club's Under-18s

Llewellyn joined Colchester United as their Under-18s lead coach in July 2017.

Llewellyn left Colchester at the end of June 2019 to become Head of Coaching at Welsh Premier League side Carmarthen Town.  He will also look after the FA of Wales' skill acquisition programme, developed by the FAW Trust.