Dónal de Róiste, who was exonerated by the Government after being forced to retire from the Defence Forces in 1969, said he was "overcome" when he received an apology this week.
He said he was "so relieved", adding that "justice delayed is still justice".
Mr de Róiste thanked "everyone who stood by me all these years".
He made the brief remarks surrounded by his family outside the gates of Leinster House following an apology by Minister for Defence Simon Coveney on Wednesday.
Alongside Mr de Róiste, his sister, campaigner Adi Roche, said all her family wanted was to have its good name restored.
She said her brother was denied due process and there was no trial or charge when he was forced to retire 53 years ago.
She added her late mother had fought for justice for her son since 1969.
Ms Roche said Mr de Róiste was "shattered" the decision by the Dáil 53 years ago and had lost everything including his "good name and character".
She said the apology this week redressed the imbalance by that decision.
She also thanked the President Michael D Higgins for his role in clearing her brother's name.