Fielden, 33, who won the last of his eight caps for England against Australia in the 2010 Four Nations Series, is now set to play against his former national side in the second round of group matches.
Aston told Rugby League World magazine: “Stuart has committed to the cause and will bring vast experience from playing at the highest level.
“There will be certain instances in the World Cup when he will be massive for us and he will add the steel and presence that we want at that level.
“I’m highly delighted that he’ll be with us.”
Fielden, who also won 25 caps for Great Britain, is currently sidelined with a knee injury but is expected back well before the end of the Super League season for club side Huddersfield.
He will be joined in the Irish ranks by a host of leading Super League stars, including Pat Richards (Wigan), brothers Scott and Simon Grix (Huddersfield Giants and Warrington respectively), Damien Blanch (Catalan Dragons) and Shannon McDonnell (Hull FC).
“Ben Currie is a big one for us – he has a massive future in the game,” Aston said.
Dave Allen (Widnes Vikings) and Warrington trio Chris Bridge, Ben Harrison and Gareth O’Brien are among other Super League players that will be included in Ireland‘s initial squad, which will be captained by Featherstone scrum-half Liam Finn.