From 1996 to 2002, Armitage lived in Roquefort-les-Pins on the French Riviera and from the age of 12 Armitage began playing for Rugby Nice Côte d'Azur Université-Racing. Armitage was rejected by the France Under-16s, who claimed he was too tall and skinny. On his return to London, Armitage joined Richmond before London Irish offered him a professional apprenticeship. Armitage joined the Academy in 2002, where he played for the England U19's and was involved in the team that won the U19's National Cup (02-03). From there he progressed to the U21 squad. His talent was recognised and Armitage played for England in the IRB World Sevens tournament 2005. In August 2009 he took part in the Middlesex Sevens tournament in Twickenham where he helped London Irish to victory over Samerai International to take the championship. In May 2013 he scored Toulon's only try of the match as they won the 2013 Heineken Cup Final by 16-15 against Clermont Auvergne.
On 8 November 2008 Armitage made his full England debut against the Pacific Islanders at fullback following injuries to Mathew Tait and Nick Abendanon. He put in a man of the match winning performance setting up a try for winger Paul Sackey. English Rugby legend and team manager Martin Johnson described Armitage's debut performance as outstanding. Armitage was one of the few England players to warrant any praise during the 2008 Autumn Internationals in which England lost three out of their four matches. Armitage scored his first international points with a 45-meter drop goal against Australia.
On 3 February 2009, Armitage and his brother, Steffon Armitage, were both named in England's starting XV to take on Italy in the opening game of the 2009 Six Nations. The ninth pair and the first time since Rory Underwood and Tony Underwood stepped onto the field together in 1995 that two brothers have played in the same England team.
In the next match, in the 2009 Six Nations Championship he scored his first try against Wales at the Millennium Stadium. He also scored a penalty and a try in England's 14–13 loss against Ireland at Croke Park. Armitage scored his third England try in as many games when he touched down against France at Twickenham, in a match England went on to win 34–10. He celebrated his try by kissing the England badge on his shirt, quite possibly to highlight his snub by the France Under-16s.
He played in England's two test matches against Argentina, scoring two tries in the first test.
Armitage's stepfather John played rugby for Hatfield and encouraged his sons to such an extent that four of them are now professional players. Guy plays for Wasps RFC while Steffon plays for Section Paloise. Bevon left RFU Championship club Doncaster Knights in 2010 for his brothers' youth club Rugby Nice Côte d'Azur Université-Racing. He is back a Doncaster from the 2013-14 season. Armitage is the first native West Indian to play rugby union for England. He has two children with Jemma, whom he married in May 2012, a son Cameron (born 2007) and a daughter Chloe (born May 2009). He is a Queens Park Rangers fan.
Away from rugby, Armitage enjoys cricket and tennis. His hero is former All Blacks blindside flanker Jerry Collins.
December 2014: Delon Armitage lands 12-week ban after Toulon full back is found guilty of verbally abusing Leicester fans
May 2013: Calls former England hooker Brian Moore a ‘fat p***k’ and tells him to ‘Go write another s*** book’ in response to criticism of his goading try celebration in the Heineken Cup final.
January 2012: Arrested for an alleged altercation outside a Torquay nightclub in the early hours of a Sunday morning. A local man was allegedly left with a split lip after the run-in.
November 2011: Banned for five weeks after striking Bath lock Dave Attwood and committing a dangerous tackle on winger Tom Biggs - his third ban for foul play within six months, including a suspension in the World Cup quarter final.
January 2011: Banned for eight weeks after verbally abusing and pushing a doping official following London Irish’s 25-24 defeat by Bath on New Year’s Day.