A search of the plane and baggage at Shannon airport found nothing alarming, and the security alert was ended shortly before noon, Aer Lingus said.
The 239 passengers aboard the plane, Aer Lingus flight 112 from John F. Kennedy airport in New York, were evacuated during a scheduled stop at 0650 GMT at Shannon, said airport spokesman Eugene Pratt.
The threat "came to a police station in Dublin, and referred to some explosives aboard that specific flight," Pratt said. Aer Lingus said police received the call at about 0300 GMT.
Dick Butler, head of ground operations with Aer Lingus, said a man with a strong Dublin accent told Gardai there was a liquid explosive on board the aircraft.
No trace of explosives was found in the initial search, and all baggage was cleared for an onward flight to Dublin, said Gillian Culhane, an Aer Lingus spokeswoman in Dublin.
"All passengers disembarked the aircraft and were interviewed in the terminal building," Aer Lingus said in a statement.
"Security authorities carried out a full security scan of the aircraft. Following a full search of the aircraft the security alert was stood-down at 11:47 a.m. (1047) and the aircraft has returned to service," Aer Lingus said.
"It wasn't an emergency landing. It wasn't a red alert. The flight was coming here anyway," Pratt said. The aircraft was parked at a remote stand as a precaution, he said.
Passengers who were ticketed to go on to Dublin had all been cleared to continue their flight by 0945 GMT, said Gillian Culhane, an Aer Lingus spokeswoman in Dublin.
Pratt said security officials decided to remove all of the baggage from the flight to be screened again.
"The passengers that were booked on the flight to Dublin, they have been reaccommodated on another flight," Culhane said.