The plaque is for Michael J Dunphy, killed in the bombing of the Sir Galahad in the 1982 Falklands War, and Lee T Davies and David M E Greenhalgh who died in the 2001-2015 war in Afghanistan.
Cllr Paul Hinge, Ceredigion County Council’s Armed Forces Champion, said: “These men from Cardigan gave their lives as they served their country.
“I am delighted that the community has had the chance to commemorate them and show their appreciation.”