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.
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.
Delon Armitage