It is 30 years since the attack at the Cenotaph in Enniskillen, Co Fermanagh, killed 11 people outright and left 68 injured, while a 12th victim, Ronnie Hill, died after spending 13 years in a coma.
Mr Varadkar was continuing the tradition of his predecessor, Enda Kenny, in attending the Remembrance Sunday ceremony.
DUP leader Arlene Foster, Northern Ireland Secretary James Brokenshire, and PSNI chief constable George Hamilton also laid tributes.
The US government’s representative in Northern Ireland, Dan Lawton, also placed a floral wreath beside the monument to the fallen.
He helped a frail, elderly veteran by the arm.
Various military representatives placed tributes.
A band played the ‘Last Post’ and the street was thronged with onlookers.
The event remembers those who died in the First World War, Second World War, and later conflicts.
Afterwards, a service was held in St Macartin’s Cathedral in Enniskillen.
Senior officials at the Catholic diocese in the town have moved to reassure all members of the community amid a row about the proposed location of a memorial to the 1987 Enniskillen bombing.
Rt Rev Joseph McGuinness, administrator for the Diocese of Clogher, said the church had “no objection whatsoever to a permanent memorial being erected to the victims”, and that it would carefully consider an application to site it on church land.
His remarks came amid fears that community relations between Protestants and Catholics could be damaged in the town amid a row over the placement of a memorial for the atrocity.
On the precise 30th anniversary of the bomb on Wednesday, a temporary memorial was unveiled to the 12 victims but quickly moved pending a decision on its future.
Meanwhile, police in the North said “cowards” who prompted a bomb alert near a cenotaph are “sickening”.
A suspicious object was discovered yesterday morning in Omagh, Co Tyrone, and the area was closed off.
PSNI chief inspector Graham Dodds said: “This is a sickening attempt by cowards to create fear and disruption on a day when many gather to pay their respects to the brave men and women who paid the ultimate sacrifice, and must be unreservedly condemned.”