Spanish defender Carlos Cuellar joined Norwich on 20th August 2014 along with striker Cameron Jerome. The 32 year old defender signed a one year contract with Norwich. He was Norwich manager Neil Adams' fourth signing of the summer.

Born in Madrid, Cuéllar began his career in Madrid playing at regional teams like C.D. Pegaso and San Federico. He played for Segunda División B side CD Calahorra in the 2000–01 season. He moved up one level in 2001, as he joined CD Numancia in the Segunda División. Two seasons later, he joined CA Osasuna in La Liga. He became an important part of Javier Aguirre's side that reached the Copa del Rey final in 2005 and finished fourth in the league in the following season, thus qualifying for the UEFA Champions League.

Scottish club Rangers made two offers for Cuéllar in June 2007 that were rejected by Osasuna, but the eventual transfer was completed on 5th July 2007, for a fee of £2.37 million. He made his competitive Rangers debut against FK Zeta on 31st July 2007, in a 2–0 victory. After impressing early in the season, Cuéllar was awarded the Scottish Premier League Player of the Month award for August 2007. He scored his first Rangers goal on 1 September 2007, during a 4–0 victory over Gretna FC. Cuéllar collected the Scottish Premier League Player of the Year award and was named the Scottish Football Writers Associations Player of the Year. He won the Scottish Cup, Scottish League Cup and reached the final of the UEFA Cup with Rangers.

On 12th August 2008, English Premier League side Aston Villa signed Cuéllar in a deal worth £7.8 million on a four-year contract. Villa's offer had triggered a release-clause in Cuéllar's Rangers contract. He had played 36 times for Rangers. Cuéllar made his official first team début on 18th September in the 3–1 UEFA Cup first round victory against PFC Litex Lovech in Bulgaria. He made his first league appearance for Aston Villa in the West Midlands Derby match against West Bromwich Albion on 21st September 2008.

He left Villa in May 2012 at the end of his contract having made 123 appearances. On 2nd July 2012, Sunderland confirmed the free signing of Carlos Cuéllar on a two-year contract following his departure from Aston Villa, signed by his former Villa manager Martin O'Neill. He made his debut on 18th August in a goalless draw against Arsenal and scored his first goal for the club on 18th Novemberin a 3–1 victory at Fulham.

At the end of the 2013–14 season, he was released by Sunderland having made 30 appearances, scoring once. He trialled with Blackburn before joining Norwich.

Cuellar made his debut in Norwich's 3-1 win over Crawely in the Capital One Cup on 26th August 2014, unfortunately scoring an own goal. He was released at the end of the season having made ten appearances

On 11th August 2015, he signed for Spanish side Almeria

n 12th August 2016, Cuéllar signed a year deal with Israeli side Maccabi Petah Tikva for an undisclosed fee. They finished third in the regular season but in the Championship round they finished fourth, missing out on the Europa League.

On 22nd May 2017, he moved to fellow Israel Premier League side Hapoel Ironi Kiryat Shmona. They are based in the Israeli city of Kiryat Shmona in the north of the country. He moved to his third Israeli club on 15th May 2018, joining Beitar Jerusalem

Released by Beitar on 16th August 2018, he joined Bnei Yehuda on 7th September 2018. He left the club in the summer of 2019 and announced his retirement on 17th October 2019.