The Yes side started to celebrate in the RDS last night as results from the seven electronic constituencies showed a strong swing in favour of the treaty.
"It's a fantastic day for Irish politics. This electorate here is one of the most sophisticated in the world," the Minister for Education Mr Noel Despsey said following the announcement of the results.
"I'm just determined not to be triumphalist about this because I've learned a lot during this campaign," he added.
The Tánaiste Ms Harney said: "I'm delighted. I think its a great result."
When asked about the difference between this referendum and last year's she said: "I think the people were better informed and I think that certainly was the crucial difference between this and the last occasion."
The Green Party's Ms Patricia McKenna, who campaigned for a No vote, conceded defeat and said "the people have spoken and we will have to accept their decision".
"As a democrat, unlike the Government, I would accept the result. If that's the result the people have voted they have made their decision, and their decision should be respected," she said.
Mr Justin Barret of the No to Nice coalition called it a sorry day for democracy saying: "The Irish people were put under enormous pressure. They were bullied and threatened throughout the campaign and if they have succeeded by this method then really its a very sorry day for democracy."
"The Irish people's will has been overturned by bullies threats and lies its just astonishing to me," he added.
Mr Joe Higgins of the Socialist Party warned that the issues raised during the campaign had not gone away and would still be very important over the next few years.
"I think key issues we raised in the course of the campaign the threat of the privitisation of public services in the future, the thrust towards militarisation of the EU and the erosion of the democratic influence of ordinary people in the member states, those will continue to be very live issues over the next years, they have not gone away."
"I think many people reluctantly this time cast a yes vote" he said when comparing the result to last year's referendum.
Meanwhile the former taoiseach Dr Garret FitzGerald, who campaigned for a Yes vote, said he was "overwhelmed" by the result.
"I thought we'd win, I thought it was like 60-40 but it looks like being much bigger than that," he said.
"It shows if you run a good campaign it makes the difference. We had no campaign last time and I do think towards the end people were getting very fed up with the number of things being said by the No people which turned out to be untrue," he concluded.
