Gabbidon began his career at West Bromwich Albion, joining as an apprentice in November 1996 before turning professional in July 1998. He made his Albion début in a 1–0 home defeat against Ipswich Town on 20 March, 1999 and, utilised as a right-back, he went on to make 27 appearances for West Brom in all competitions. Following the appointment of Gary Megson as manager towards the end of the 1999–2000 season, Gabbidon failed to keep his place in the team. Megson switched to a 5-3-2 formation, signing Des Lyttle to fill the right-wingback position. Gabbidon joined Cardiff City on a one-month loan at the start of the 2000–01 season.
Gabbidon signed a permanent four-year deal with Cardiff City in September 2000, for a fee of up to £500,000 depending on appearances and future honours. His performances in the 2001–02 season helped Cardiff to the Division 2 play-offs, saw him make his senior international debut for Wales in March 2002 and win the Welsh clubman of the year award in October 2002. He signed an extension to his contract in April 2002, saying that it was the prospect of exciting times ahead that had persuaded him to do so. A back injury that had troubled him for some years, forced him off the pitch during a match against Barnsley in November 2002 and it was not until April 2003 that he returned to competitive action in a reserve game. He returned to the first-team in time to help Cardiff win promotion to Division 1 through the play-offs in May 2003. He missed several games at the beginning of the 2003–04 season with a heel injury but his assured performances at centre-half, and those of striker Robert Earnshaw, led club chairman, Sam Hammam, to insist in December 2003 that "Our top young players are going nowhere" in the January 2004 transfer window. Gabbidon went on to earn a place in the First Division team of the year in April 2004. Despite speculation during 2004 that Gabbidon might leave Cardiff City, Gabbidon signed an extension to his contract in September 2004, tying him to the club until 2008. Cardiff were prepared to offer him "...the most lucrative contract ever offered to a Cardiff player", with club owner, Sam Hammam, saying, "I want to make Danny Gabbidon a cornerstone of Cardiff City FC, I see him as the absolute future of this football club personified." The 2004–05 season saw Cardiff embroiled in a relegation battle in the first half of the season, something to which Gabbidon was unaccustomed. An unbeaten run in January 2005 however saw Cardiff lift themselves five points clear of the Championship relegation zone and Gabbidon named the Championship's player of the month. A financial crisis at Cardiff at the end of the season led to Gabbidon being unsure of his future at the club and he was sold to West Ham in July 2005 to help cut the wage bill.
Gabbidon moved to West Ham in July 2005, as part of a deal that also took fellow defender James Collins to Upton Park. His performances for his country during the year won him the Welsh Footballer of the Year award in October 2005. He established himself in central defence alongside Anton Ferdinand and helped West Ham to a mid-table position in the Premier League in the 2005–06 season and to the FA Cup final in May 2006, receiving a runners-up medal. After his performances in the 2005–06 season, he was voted 'Hammer of the Year' with Marlon Harewood named as runner-up. Gabbidon had been ever-present as West Ham struggled against relegation in the 2006–07 season, when he suffered a torn hamstring in November 2006, which sidelined him for a month. Groin injuiries required surgery in January 2007 and again in April, ruling him out for the rest for the season. West Ham started the 2007–08 season with Anton Ferdinand and Matthew Upson in the centre of defence with Gabbidon as substitute. He signed a two-year extension to his contract in August 2007, saying, "I am disappointed not to be in the side but at least the new contracts show that the club wants both me and James [Collins] around. We will both now work hard and fight to prove we are worthy of a place in the side."
Gabbidon had made 17 appearances for the Welsh Under-21 team, when an unexpected call up for the Welsh senior squad in the World Cup qualifier against Belarus in October 2001 prevented him from making his final appearance for the under 21 side. He was an unused substitute in that match and was again called into the senior squad for a friendly game against Argentina in February 2002 but it was not until the next month that he made his debut in a 0–0 home draw against the Czech Republic. He became a regular in the team despite a back problem that caused him to miss a large part of the 2002–03 season, and was part of the squad that narrowly missed out on a place at Euro 2004, losing to Russia in the play-offs, and the squad that did not qualify for the 2006 World Cup. Roy Evans, the Wales assistant coach, tipped Gabbidon to be a future captain of the national side, saying, "I see him as potential captain material even if it is not my decision. But he has all the qualities. You do not always have to be vocal, you need to lead by example." Gabbidon captained the side in place of the injured Ryan Giggs in 1–0 away defeat against Cyprus in November 2005 and again in place of Craig Bellamy in a 1–0 win against Bulgaria in August 2007.
With West Ham United
Football: Wales V Azerbaijan European Championship: Put Your Shirt on Me Getting Another Prize; Says Danny Gabbidon
Nov 20, 2002; Byline: Martin ROGERS DANNY GABBIDON is starting to pay the price for his amazing rise to prominence under Mark Hughes. Cardiff...