After the country rejected the charter last June, Irish Taoiseach Brian Cowen insisted the 67.1% "Yes" vote in the referendum re-run was a declaration of intent to stay at the heart of Europe.
Mr Cowen said: "It is a good day for Ireland, it is a good day for Europe."
The Taoiseach refused to be drawn on the scale of damage to Ireland's reputation from last year's defeat and how much work was needed to restore its standing with EU neighbours.
"To the question of what damage was done at that time to the Irish, I think there was respect for the democratic process and the fact that it couldn't be overturned without returning to the democratic process," Mr Cowen said.
Mr Cowen said legal guarantees hammered out earlier this year helped public opinion swing towards a Yes, but accepted the economic threat of distancing the country from Europe played a key role in the run-up to the ballot.
"What's important to point out is that Ireland has always been a core Euro-positive country," he said.
"It is a country that acknowledges, recognises and appreciates the benefits that membership has brought."
More than 1.2 million people voted in favour of the treaty this time round - a 20% swing since the shock rejection last year.
Only the two Donegal constituencies on the north-west tip of Ireland said "no" on this occasion.
European Commission president Jose Manuel Barroso spoke by phone to the Taoiseach to congratulate him on the result.
Sporting a carefully-chosen green tie, Mr Barroso welcomed the resounding win from Brussels.
"The Irish people have spoken. They have said a resounding Yes to Europe. Thank you Ireland. It is a great day both for Ireland and for Europe," Mr Barroso said.
Prime Minister Gordon Brown also welcomed the emphatic result.
Only Poland, which is expected to rubber stamp the treaty within days, and the Czech Republic, where there is a legal challenge, have yet to formally ratify the reform deal.
The last 15 months saw a massive turnaround in public opinion following assurances from Brussels on the key concerns of Irish people - tax, neutrality, abortion and retaining a Commissioner.
But worries over the economy also formed a decisive part of campaigning over the last four weeks.
Multi-millionaire businessman and unsuccessful European candidate Declan Ganley claimed voters had made a mistake and branded the "yes" campaign dishonest.
"I'd like to say it was inspired by hope but I fear that it was not, but I respect the outcome," Mr Ganley said after his second attempt to derail EU reform failed.
Asked about campaigning "scare tactics", Mr Barroso responded: "Any campaign of fear was generated by the No campaign, with tactics such as posters about a minimum salary being imposed on Ireland by Europe."
Despite seething anger at the coalition Government over Ireland's property crash, banking crisis and subsequent recession, opposition politicians claimed voters put distrust behind them to act in the national interest.
Labour leader Eamon Gilmore seized on the opportunity declaring: "The national interest now requires that this Fianna Fail government be removed from office as quickly as possible."
The "no" camp - which included a array of activists from Socialist MEP Joe Higgins to the UK Independence Party, Sinn Fein and lobby group Coir - demanded the Government deliver on commitments that Lisbon will deliver jobs.
The Lisbon Treaty, born out of the rejected European Constitution, was billed as reform to streamline decision making in Brussels.
It will create a president of Europe, an EU foreign minister, reduce a state's ability to veto and increase powers in the Commission.
One of the most emotive issues in the campaign was sparked by posters from lobby group Coir, which suggested Ireland's minimum wage would be slashed by the reform package to as low as 1.84 euro (£1.68).
Voters rejected the concerns and out of an electorate of 3.1 million and 58% turnout more than 1.2 million backed Lisbon.
There was a margin of more than 600,000 between the "yes" and "no" camps.
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