On Tuesday, less than a year after stunning this British territory by making peace with his enemies, Paisley declared his lifetime's work done. His words came whisper-soft at times, confident and content.
His decision to form a government alongside a former Irish Republican Army commander, he said, "was the right thing to do."
The 81-year-old evangelist announced he would quit in May as leader of the fledgling Protestant-Catholic government and also would surrender the reins of the Democratic Unionist Party he founded 37 years ago.
Analysts, colleagues and opponents universally called it the end of an era.
Paisley said he picked his May departure because he will be able to preside over an international investment conference in Belfast featuring potential U.S. investors.
He also expects praise in April from a string of visiting dignitaries, including former British Prime Minister Tony Blair and former President Clinton, when Northern Ireland commemorates the 10th anniversary of the U.S.-brokered Good Friday accord - a power-sharing plan that Paisley initially opposed.
Only a few years ago, the idea of Paisley cooperating with the leaders of the IRA-linked Sinn Fein - people he denounced as "bloodthirsty monsters" in alliance with the devil - seemed an impossibility.
But the anti-Catholic preacher responded decisively after winning a string of key concessions from his enemies: the IRA's 2005 disarmament and renunciation of violence, and Sinn Fein's 2007 vote to accept the authority of the Northern Ireland police.
Ever since Paisley began leading an administration alongside veteran IRA commander Martin McGuinness, observers had waited in vain for them to trade insults and split. Instead, the pair appeared joking together frequently in public and become widely known as the "chuckle brothers."
The British and Irish governments - who long dismissed Paisley as a hate-monger and destructive bigot and froze him out of negotiations from 1998 to 2003 - praised him Tuesday as the one figure powerful enough among Protestants to make stable power-sharing with Sinn Fein work.
"Was there anyone else who could have carried it? I very much doubt that," said Irish Prime Minister Bertie Ahern, who forged a warm public relationship with Paisley over the past year of growing all-Ireland cooperation.
"Ian Paisley's contribution to peace, after all the years of division and difference, was decisive. ... The man famous for saying 'no' will go down in history for saying 'yes,"' said Blair, who together with Ahern oversaw Belfast negotiations that produced the Good Friday pact.
Paisley, who founded his own Free Presbyterian Church of Ulster in 1951, emerged in the 1960s as Northern Ireland's most charismatic anti-Catholic cleric. He was imprisoned in 1968 for leading Protestant mobs against Catholics' demands for equal rights in housing, voting power and employment.
In 1969, as Britain deployed troops as peacekeepers, Paisley said Catholics "breed like rabbits and multiply like vermin," and accused Catholic priests of distributing guns to the fledgling IRA.
He played a leading role in orchestrating mass Protestant strikes that forced the collapse of Northern Ireland's first Protestant-Catholic government in 1974. He gained international attention by heckling Pope John Paul II at the European Parliament in 1988, when he shouted "I denounce you, antichrist!" at the bemused pontiff. His booming oratory served to whip up Protestant mobs well into the 1990s.
Long a hate figure to Catholics, their leaders came in recent years to appreciate his strength and personal warmth. Paisley, in turn, visibly mellowed in his relations with Catholics, meeting church leaders and desisting from insulting them in public.
In a foreshadowing of Tuesday's announcement, Paisley in January stepped down as leader of his church, reflecting divisions among the Paisley faithful over his relations with Sinn Fein.
"I have found him to be very personable and good-humored," Sinn Fein leader Gerry Adams said after hearing of Paisley's retirement plan.
Asked whether Paisley's departure from atop the government could spell trouble for its survival, Adams said, "There'll only be instability if those who don't want progress get into the ascendancy."
The Democratic Unionists said the party's members in the Northern Ireland Assembly would pick a successor, but set no date for the vote.
Paisley said he would play no role in anointing a successor - and took a jovial swipe at his oldest enemy.
"This is not the Church of Rome," he said, chuckling. "This is not apostolic succession and I have no right to say who will succeed me."