In 2010, ex Scotland and then Motherwell manager Craig Brown, stated Carey "looks a real talent" and said he "is the kind of player fans like to watch"
In 2005, Carey signed for Celtic from Shelbourne's youth set up. He made his senior Celtic debut as a substitute against Rapid Vienna in the Europa League on 17 December 2009, a match which Celtic drew 3–3. He was regularly named as a substitute for Celtic in the 2009–10 SPL season before being loaned out to St Mirren in February 2010, and English League One team Huddersfield Town in August 2010.
Carey was a regular for the youth team and reserves during his time in Glasgow and worked under Willie McStay, Danny McGrain and Neil Lennon. He later said he was disappointed to have never made it into the first team during his time at Celtic.
In a bid to get more first team experience for Carey, Celtic boss Gordon Strachan loaned him out to League of Ireland Champions Bohemians in February 2009. He played his first league match against Derry City on 13 March and scored his first league goal against St. Patrick's Athletic on 11 April. Carey was deemed an instant hit and was described as the star of the show having impressed during the local derby against St. Patrick's Athletic.
Bohemians manager Pat Fenlon was keen to extend Carey's loan deal which expired in July until the end of the season. The talented winger was also due to be out of contract at Celtic in July and was aiming to secure a place in new manager Tony Mowbray's team due to impressive performances with Bohemians and the Republic of Ireland under 21s.
Carey was due to play on the left wing in Bohemians' Champions League qualifiers against the Austria Champions Red Bull Salzburg, but the loan deal could not be extended in time. He made 20 appearances and scored five goals in all competitions for Bohemians and capped his loan period by winning a League of Ireland Medal.
Carey joined St Mirren on loan on 1 February 2010, until the summer of 2010. He made his debut against St Johnstone on 10 February in the SPL. He came on as a 60th-minute substitute and curled in a free kick which led to the equalising goal for Michael Higdon. He was described as having "impressed" on his debut. Saints manager Gus McPherson said in his post match interview "Graham Carey had some good delivery from the wider area. He's only been with us for a week and we hope he'll be a good addition for us."
Carey scored his first goal for St Mirren on 6 March 2010, when he scored from a free kick against Rangers. After the match, he said he copied Cristiano Ronaldo's free kick technique. A few weeks later, Carey started against Rangers, in the Scottish League Cup Final, but the match ended in a 1–0 loss for St Mirren.
Carey scored a 35-yard free kick against Hearts in the SPL on 3 April, and was commended by the St Mirren manager Gus MacPherson who said "It was a wonder strike from Graham. When he picks up the ball there's excitement as the crowd sense something may happen. He's always more than capable with his excellent delivery from set-pieces." On 24 April 2010, Carey helped set up the winning goal for Andy Dorman as St Mirren beat Kilmarnock 1–0 and after being substituted, received a standing ovation from the St Mirren fans.
Carey won the SPL Young Player of the Month award for April 2010 and St Mirren manager Gus MacPherson added that he was keen to keep him at the club. His successful loan spell at St Mirren attracted interest from Premier League clubs Wigan Athletic, Wolves and Blackpool as well as Ipswich Town in the Championship. He was offered a two-year contract extension by Celtic.
On 14 July 2010, Carey signed on loan for League One outfit Huddersfield Town until January 2011. Huddersfield boss Lee Clark said "Graham will bring brilliant versatility to the squad – he can play anywhere up the left side of the pitch.... He has a terrific left foot and he looks as elegant as you would expect from a quality left-footed player". Carey made an immediate impact with Huddersfield scoring a low left footed drive from 20 yards against Bury in a pre-season friendly on 19 July 2010.
He made his first appearance for the Terriers as a substitute in a 1–0 win against Carlisle United at Brunton Park in the League Cup. He made his first League One start in the 4–2 loss against Peterborough United at London Road Stadium. Carey while playing as a left back, provided an assist to Jordan Rhodes from a well worked corner and scored a 25-yard free kick to make the score 2–0 to the Terriers. On 28 August 2010, he started for Huddersfield against Charlton Athletic, on the left side of midfield and was awarded Man of the Match for his efforts, including setting up two goals during the match.
Huddersfield manager Lee Clark wanted to keep Carey after his loan deal expired in January 2011, but despite talks of extending the deal to the end of the season, terms were not agreed, and he returned to Celtic. He made 23 starts and three substitute appearances for the Yorkshire club, scoring two goals.
On 8 July 2011, Carey re-signed for St Mirren permanently, having had a successful loan spell in the 2009–10 season. St Mirren Manager Danny Lennon said: "It's great to get Graham in. I believe in wider areas we let ourselves down last season and he has a left foot to die for. That type of quality is very scarce. He's an intelligent footballer and will be a major addition to the squad. He is very good in dead-ball situations." On 11 December 2011, Carey scored what was described as a "blistering free kick" to earn St Mirren a point against Aberdeen. He scored again for St Mirren to earn another draw against Dundee United on 28 December 2011 and also provided the assist to Thompson for the first goal in a 2–2 draw. Following the match, the club's supporters named Carey as the Paisley ‘Ronaldo’. A few week later, on 17 January 2012, Carey scored in the fourth round replay of the Scottish Cup, in a 1–0 win over Hamilton Academical, to send the club through to the next round. In the quarter final of the Scottish Cup, he scored against Hearts, in a 2–2 draw to earn a replay.
In the 2012–13 season, Carey missed the opening game of the season, due to a hamstring problem. In the Scottish League Cup Final, Carey come on a substitute in the 81st minute for John McGinn, as St Mirren won 3–2 against Hearts, winning the trophy for the first time. He said winning the League Cup was "great experience". On 13 May 2013, Carey's goal against Hearts in February 2010, was voted as the Scottish Premier League goal of the Season for 2012–13. The goal has been described as an astonishing wonder goal, which was a 35-yard strike after he collected the ball from his own half, played a one two then hits the top right hand corner. At the time of the goal, Carey's shooting skill was praised by Lennon. while he described it himself as a "wonderful strike".
On 15 May 2013, it was confirmed that Carey would be released at the end of the season by St Mirren along with Sam Parkin. Following his release, sources revealed that Carey had wanted to leave the club in January and had request a transfer, but this was rejected. He was also linked a move to England to kickstart his career.
After leaving St Mirren, Carey went on trial with Dundee United After three weeks at the club, Carey's trial at Dundee United came to an end after the club were indecisive with their interests signing him.
On 30 July 2013, Carey, alongside Brian McLean joined Ross County. He made his debut, in the opening game of the season, a 2–1 loss against Celtic In the next game, Carey scored his first goal for the club, scoring with a deflected shot from outside the area, in a 3–1 loss against Partick Thistle. He then scored his second goal of the season three months later on 23 November 2013, in a 2–2 draw against Hearts. Carey's third goal of the season came on 4 January 2014, in a 1–0 win over St Johnstone. Carey made thirty-eight appearances, scoring three times in all competitions, having missed two league games, due to injuries.
Ahead of the 2014–15 season, Carey signed a new contract with Ross County on 7 August 2014, just three days before the season started. Under the new management of Jim McIntyre following the sacking of Derek Adams after five defeats, Carey played in an unfamiliar role as a left-back. He scored his first goal of the season in a 2–2 draw against St Mirren on 25 October 2014. Two weeks later on 8 November 2014, Carey scored his second goal of the season, in a 3–0 win over Kilmarnock.
At the end of the 2014–15 season, Carey was released by the "Staggies".
On 2 July 2015, Carey signed for Football League Two club Plymouth Argyle on a one-year contract. Carey scored on his debut in a 2–0 win at AFC Wimbledon on the first day of the season. His scoring run continued with 4 goals in his first 5 league games for the club.
Carey enjoyed an excellent first season at Plymouth, scoring 12 goals in 46 games and winning the club's Player of the Year award. Carey was also included into the English League 2 Team of the Season for the 16/17 season, along with teammates Sonny Bradley and Luke McCormick, after 15 goals and 15 assists in all competitions.
On 29 June 2017, despite interest from other clubs and speculation that he could move on after his contract expired, Carey signed a new contract at Argyle keeping him at the club where he has gained cult status amongst the supporters.
Carey has represented the Republic of Ireland at youth, under-17 and under-19 level. He has six Under-21 caps. His debut for the Under-21s came under Don Givens in February 2009 at Turners Cross against Germany. He scored his first goal at that level away to Georgia with an impressive 18-yard left footed strike after a clever one two with Cillian Sheridan.
Carey's preferred and most effective position is playing as a No 10 behind the stiker, allowing him the freedom to move around the field and get on the ball. He can also play on the left or right side of midfield. He is very direct in his play and attacks defenders at every opportunity, while being a set-piece specialist his crossing has been described as "unbelievable". While at St Mirren, Carey was used as a left back and as a wing back on the left side.As of match played 8 January 2017
League of Ireland: 2009
Scottish League Cup: 2012–13
EFL League Two Team of the Year: 2016–17