The agency retained the brief following a pitch against three undisclosed agencies.
The Legion called a pitch for the business in March, stating that it wanted to use DM to help broaden its audience base. Guy Upward, the head of direct marketing and legacies at the Royal British Legion, led the pitch.
It is the second time that Tangible has successfully defended the business. It first won the account in 1998, and retained it in a pitch in 2003.
The Cheltenham-based agency has created mailpacks focusing on donor development, as well as raising awareness of the charity's work for Remembrance Day. It also created a special edition of its magazine Poppy Press, to commemorate the 90th anniversary of the end of the First World War.
The Gate, which is the incumbent on the Legion's above-the-line account, is unaffected by the appointment.