With polls set to open open, they said Europe without Britain would be unimaginable to them.
The rockers made a direct appeal to fellow country men and women voting in the referendum to back Remain.
On their official Facebook page, they reposted a video showing barriers coming down and bridges being built in Ireland since the peace process.
The video by the Ireland4Europe campaign warns of the risk that new border controls would bring an end to all the progress made over 18 years since the Good Friday Agreement.
In the event of a Brexit, the now seamless border between the North and the Republic of Ireland would become the only land frontier between the UK and Europe.
“We were asked to repost this video,” U2 said on their fan site. “We like it and we’re humbled to be in it.”
“For Irish voters in Britain, don’t go we’d miss you ... Europe without Britain seems unimaginable to us. Bono, Edge, Adam and Larry.”
Irish actor Liam Neeson OBE also lent his support to the Remain camp, warning of the “worst” ramifications for Ireland in the event of Britain opting out.
“I would like to lend my voice to Irish4Europe’s campaign to encourage Irish citizens to vote for the UK to remain in the EU,” he said in a statement.
“A UK exit would have the worst ramifications for the island of Ireland. Economically, this would be a backwards step for Ireland.
“Border controls would be implemented to allegedly stop illegal immigrants coming into the UK through the backdoor. Trade will be enormously impacted.
“It would be truly a shame to sacrifice all the progress that has been made by the peace process regarding border controls.
“There is strength in unity. A Brexit vote will make us weak. I urge you to go out and vote to remain in the EU.”
Irish voters represent up to 10% of the UK electorate.
With the Remain and Leave sides neck and neck, their role could be critical in the outcome of Thursday’s poll.
David D’Arcy, of Irish4Europe, pleaded with each and every Irish voter to make voting Remain their first task on the day.
“Don’t leave it. In such a close race, the Irish could make the difference,” he said.
World leaders also added their voices to the debate during the campaign.
US President Barack Obama said Britain is “at its best when it’s helping to lead a strong European Union” and warned that the UK would be at “the back of the queue” for American trade deals if it left.
Japan’s prime minister Shinzo Abe said Brexit would make the UK “less attractive” to Japanese investors. New Zealand’s prime minister John Key said his government believes “it’s a stronger position for Britain to be in Europe”.
Canadian prime minister Justin Trudeau said there is “nothing easy” about forging trade deals outside the EU and said Britain’s clout is “amplified” by being a member of the bloc.
German chancellor Angela Merkel said the decision is up to UK voters but added: “I personally would hope and wish for the UK to stay part and parcel of the EU”.
Indian prime minister Narendra Modi described the UK as the “gateway to Europe’’ and said a “united Europe would be favourable’’.
Russia’s president, Vladimir Putin, has refused to put on record what outcome he would like to see but said David Cameron had called the vote “to blackmail Europe’’.