The Spartak Moscow man has become the fifth player ruled out of Giovanni Trapattoni's squad for the Cardiff friendly.
An FAI statement read: "The Football Association of Ireland today confirmed that Aiden McGeady has withdrawn from the Ireland squad to face Wales in Cardiff on Wednesday, August 14 after sustaining a knee injury during training with Spartak Moscow."
McGeady, 27, has won 60 caps for the Republic, scoring just twice.
Fellow winger Anthony Pilkington of Norwich headed up Wednesday's list of withdrawals, also due to a knee injury, while Hull's Stephen Quinn (hamstring) is also absent from Trapattoni's midfield options.
An ankle injury accounted for Nottingham Forest forward Simon Cox while Millwall goalkeeper David Forde (knee) was replaced by West Ham's Stephen Henderson.
Yeovil forward Paddy Madden was last night placed on standby, but today's statement merely revealed: "Updates will be issued in due course should a replacement be added to the squad."
Trapattoni's initial 26-man squad saw no place for experienced strikers Robbie Keane and Kevin Doyle and defender Richard Dunne.