The Wigan Athletic midfielder has taken the decision to withdraw from contention for the summer tournament due to a family issue
The midfielder was originally due to be part of Giovanni Trapattoni's 23-man squad for the tournament this summer in Poland and Ukraine but the Italian revealed at Monday's press conference that McCarthy took the decision to withdraw.
"Last week, he called me. He told me what happened in his family," Trapattoni told the assembled press.
"I said to him 'I'm sorry, I'm very very sorry'. He has decided to stay at home because he has a very heavy duty to his parents."
Trapattoni has also assured McCarthy, 21, that he will be part of Ireland's World Cup qualification campaign which begins in the autumn.
"I said, 'You are in our plans for the future'.", Trapattoni revealed.
The FAI issued a statement on behalf of McCarthy regarding his father's health.
“I have made the very difficult decision to withdraw my name from selection for the Euro 2012 squad following the diagnosis of my father with cancer and an on-going requirement for treatment.
“I have discussed this with the manager. He was very understanding, and I thank him sincerely for that.
“I take this opportunity to re-affirm my complete commitment to playing for the Republic of Ireland. It is a huge honour and source of great pride for me and my family. Despite not being present, I would like to wish the manager and my teammates every success at the tournament and hope that Irish fans can understand the reason for my decision at this difficult time.”