The PM has recited Rupert Brooke's poem The Soldier for the official First World War centenary album, which also includes contributions from Stephen Fry, Radio 4's Today presenter James Naughtie and Game Of Thrones actor Sean Bean.
The album of words and music, called Forever, will include appearances from the descendants of servicemen who were awarded the Victoria Cross in the war, whose voices have been assembled for a version of John McCrae's In Flanders Fields.
Mr Cameron recorded his performance inside his home at 10 Downing Street in London, including one of the most famous lines from the war poets: "If I should die, think only this of me - that there's some corner of a foreign field that is forever England."
The album will be issued by Decca Records on July 14.
Royal British Legion director of fundraising Charles Byrne said: "The poetry borne of the struggles of World War One captured so hauntingly the trauma experienced by a generation of young men."
Funds raised will go towards meeting the £230,000 daily costs of helping and supporting service personnel.