Ireland boss Mick McCarthy has decided to include the former Everton midfielder after Wolves winger Mark Kennedy was forced to withdraw from the squad with a hamstring injury.
Farrelly, who won the last of his six caps in the 1-1 draw with the USA in Boston in June last year, will join up with the rest of the squad on Wednesday.
Meanwhile, McCarthy is confident that captain Roy Keane will be fit to play, despite recently being troubled with a knee injury, which has ruled him out of the last few games for Manchester United.
"I spoke to Roy by telephone and he told me that he is fine after his recent knee injury," said McCarthy.
"Roy has been training at Manchester United and receiving treatment at the same time. But he'll definitely be traveling to Dublin."
McCarthy received another boost when Sunderland winger Kevin Kilbane took part in training after being troubled by an ankle knock.
"My ankle problem has kept me out of the game for three weeks but I felt fine and there was no reaction afterwards. I will be fit to play if selected," said Kilbane.
Ipswich midfielder Matt Holland, Fulham's Steven Finnan and Millwall midfielder Steven Reid missed the training session, but McCarthy expects them to be fit for Saturday.
"They have only minor knocks and didn't take part as a precaution. But I expect them all to be ready for action on Saturday," said McCarthy.
