Coloccini has represented numerous football clubs, but it was his successful spell at Deportivo La Coruña, where he earned his reputation as a top-level defender. After beginning his career at Boca Juniors in his native Argentina, Coloccini attracted the attention of A.C. Milan. He failed to establish himself there, however, and subsequently went on loan to four different clubs.
He joined Newcastle United in August 2008, for a fee of up to £10.3 million, and in July 2011, he was promoted to club captain, after proving himself as one of the Premier League's most reliable and strong central defenders. In April 2012, he was named in the PFA Team of the Year due to his influence in Newcastle's impressive season. On July 5, 2016, Coloccini returned to Argentina to join San Lorenzo, with whom he had previously been on loan to.
Born in Córdoba, Córdoba Province, Coloccini started his career in the youth team of Argentinos Juniors, but made his professional debut in 1998 with Boca Juniors. He made two league appearances, both from the bench, in his one and only season with Boca. He scored in his second (and final) match, leveling the scores in a 2–2 draw with Unión de Santa Fé.
In 1999, at the end of the Apertura championship, he moved to A.C. Milan. Coloccini was at the centre of a controversy between Boca and Milan, because the transfer from Argentina to Italy wasn't agreed between the clubs. Instead, Milan arranged terms with Coloccini's father (also a former football player), who exercised his parental rights to remove the minor from Argentina. After that, FIFA ordered Milan to pay Boca compensation.
In 2000, Coloccini was loaned to San Lorenzo where he helped the team to win the 2001 Clausura tournament. From 2001–04, Coloccini served three consecutive loans in La Liga: Alavés (netting an impressive 6 league goals), Atlético Madrid, and Villarreal, where he was always first-choice.
After having only appeared once for Milan officially, Coloccini joined Deportivo La Coruña in January 2005, on a six-year deal. During his three-and-a-half seasons stint, he was an undisputed starter, and appeared in all the matches during 2007–08 netting four goals, good enough for a UEFA Intertoto Cup berth for the club.
Coloccini joined Newcastle United on a five-year contract in August 2008 for a fee of up to £10.3 million. Two days later, he made his debut against the reigning league champions, Manchester United, playing 90 minutes in a 1–1 away draw.
Since his debut, Coloccini has been one of the most consistent inclusions in Newcastle's squad, and formed a partnership with fellow newcomer Sébastien Bassong in his first season. He was not immune to the pressures of representing Newcastle's infamous defence, coming under his most intense criticism for his performance in Newcastle's 5–1 defeat to Liverpool. Despite his mistakes in the game, manager Joe Kinnear voiced his support for Coloccini, stating that he believed his "Mr. Reliable" would bounce back. On 1 February, Coloccini was substituted against Sunderland in the 93rd minute. Up until this point, he had played every minute of every game for Newcastle all season. He was dropped for the 1–1 draw with Stoke City, but played in Newcastle's 1–0 defeat to Aston Villa, which saw them relegated.
Despite Newcastle's relegation, Coloccini stayed on and was the mainstay of the club's defence all season, partnering the likes of Steven Taylor, Mike Williamson, Fitz Hall and Tamás Kádár in the sturdiest rearguard of the league. He scored two goals for Newcastle since relegation, a header at Cardiff City, and another header at Watford. The club was eventually promoted back to the Premier League as champions, and Coloccini's great contributions awarded him a place in the Championship's Team of the Year. Coloccini scored his third Newcastle goal against Wigan Athletic in the fourth minute of injury time as they came from two goals down to draw 2–2 at St James' Park, with that being his first goal in the Premier League on the same day that he captained Newcastle for the first time. Coloccini scored a striker's finish in a 1–1 draw with Tottenham Hotspur on 22 January 2011, the day of his 29th birthday and his 100th Newcastle appearance.
He continued his fine form for Newcastle into April, reforming his partnership with Mike Williamson after a brief time with Steven Taylor in January. On 2 April, Coloccini made numerous forward runs and forward roaming to help supply Peter Løvenkrands' goal in the 4–1 win over Wolves. Manager Alan Pardew, along with pundit Jamie Redknapp complimented the defender for his contributions to the team's attack, calling him a "top, top player".
On 8 July 2011, Coloccini was named Newcastle captain for the 2011–12 season. He and Taylor rekindled their partnership and were central to one of the Premier League's meanest defences, conceding a mere 8 goals in the first 11 games. He scored his first goal of the season in the 122nd minute to win the game against Championship club Nottingham Forest in a 4–3 thriller in the third round of the League Cup that saw Forest equalise on three occasions. In October, he was selected for the North East Football Writers' Association Player of the Year for 2011. On 22 April 2012, Coloccini was named in the PFA Team of the Year. After an impressive display in the Tyne–Wear derby against Sunderland in October, Pardew was so impressed with the way Coloccini played that he said the performance was just like watching England legend Bobby Moore.
In January 2013, Coloccini stunned Newcastle by asking for a transfer back to Argentina citing personal reasons. His preference was to move to the team he helped win the 2001 Clausura, San Lorenzo. However, San Lorenzo could not afford his wages or the transfer fee Newcastle would want, as he still had four years left on his contract. After lengthy talks with club officials and manager Alan Pardew, Coloccini decided to stay at St James' Park until the end of the 2012–13 season and then decide on where his future lies. On 16 June 2013, Coloccini confirmed that he was staying at Newcastle until the end of the 2013–14 season at least, after lengthy talks with Pardew. Coloccini also praised Newcastle as a club, saying that they had done everything possible to make him stay. On 1 November 2014, Coloccini made his 200th league appearance for Newcastle, in the 1-0 win over Liverpool at St James' Park. Eight days later, he scored his first goal in three years, with a header in Newcastle's 2–0 away win over West Bromwich Albion.
In July 2015, Coloccini was linked with a move to Crystal Palace to link up with former manager Alan Pardew on a permanent deal. This was later publicly dismissed by Pardew, in a statement released on 5 August 2015. On 6 August, Coloccini ended speculation about his future by penning a one-year contract extension that keeps him at the club until the end of the 2016/17 season, with the option of a further year beyond that.
On 5 July 2016, Coloccini mutually agreed with Newcastle that his contract would be terminated, with him signing for Primera División side San Lorenzo that same day.
Coloccini was part of the Argentina Under-20 that won the 2001 FIFA World Youth Championship, as well as the gold medal winning Argentina team at the 2004 Summer Olympics.
With the main squad, he made his debut in 2003 and first participated in the 2005 Confederations Cup. In the 2006 FIFA World Cup, Coloccini played in two games, as a substitute against the Netherlands, and starting against Germany in the quarter-finals penalty shootout loss. Coloccini was an unused substitute in Argentina's World Cup qualifier against Brazil on 6 September 2009. He was absent from the national team in the 2010 FIFA World Cup. Due to his great form throughout 2012, Coloccini was recalled to the Argentina squad under new manager Alejandro Sabella for the FIFA World Cup qualifiers against Paraguay and Peru in September 2012. Coloccini played the full 90 minutes in a 5-2 win over Paraguay on 10 September, a game which sealed Argentina's place in the 2014 FIFA World Cup in Brazil.As of 7 July 2016
As of 14 September 2013.
Argentine Primera División: Apertura 1998, Clausura 1999
Argentine Primera División: Clausura 2001
Football League Championship: 2009–10
FIFA World Youth Championship: 2001
Olympic Gold Medal: 2004
Football League Championship PFA Team of the Year: 2009–10
Premier League PFA Team of the Year: 2011–12