O’Dowda receives his first call-up since March and he comes into the squad in place of Cardiff City striker James Collins who has been ruled out through injury.
All other players have reported for duty ahead of the first training session of the week this afternoon in Dublin.
Ireland plays Portugal on Thursday night at the Aviva Stadium before the final game with Luxembourg on Sunday.
Republic of Ireland squad:
Goalkeepers: Caoimhin Kelleher (Liverpool), Gavin Bazunu (Portsmouth, on loan from Manchester City), Mark Travers (AFC Bournemouth).
Defenders: Seamus Coleman (Everton), Matt Doherty (Tottenham Hotspur), Ryan Manning (Swansea City), Enda Stevens (Sheffield United), James McClean (Wigan Athletic), Shane Duffy (Brighton and Hove Albion), John Egan (Sheffield United), Andrew Omobamidele (Norwich City), Nathan Collins (Burnley).
Midfielders: Conor Hourihane (Sheffield United, on loan from Aston Villa), Josh Cullen (Anderlecht), Jeff Hendrick (Newcastle United), Jason Knight (Derby County), Jayson Molumby (West Bromwich Albion, on loan from Brighton and Hove Albion), Alan Browne (Preston North End), Jamie McGrath (St. Mirren).
Forwards: Callum Robinson (West Bromwich Albion), Troy Parrott (MK Dons, on loan from Tottenham Hotspur), Adam Idah (Norwich City), Will Keane (Wigan Athletic), Chiedozie Ogbene (Rotherham United), Daryl Horgan (Wycombe Wanderers), Callum O’Dowda (Bristol City).