At 11am those gathered across the UK observed a two-minute's silence in an Act of Remembrance, with poppy wreaths laid in tribute afterwards.
In Enniskillen, Taoiseach Enda Kenny joined NI Secretary of State Theresa Villiers and Fermanagh & South Tyrone DUP Minister Arlene Foster joined those marking the national day of remembrance in the town.
Twenty-six years ago, 11 people were killed and over 60 were injured in an IRA bomb at the town's War Memorial.
Mr Kenny made history last year by becoming the first Irish premier to attend a Remembrance Day service in Northern Ireland when he visited Enniskillen on the 25th anniversary of the Poppy Day bomb.
In Belfast the 2nd Battalion of the Royal Irish Regiment performed a guard of honour at City Hall's Cenotaph and Garden of Remembrance where several thousand turned out for the region's main commemoration service took place.
Among those laying wreaths were First Minister Peter Robinson, her Majesty's Lord Lieutenant of Belfast Dame Mary Peters, with tributes led by Deputy Lord Mayor Alderman Christopher Stalford.
Those who served us protected our freedom, our way of life and secured for us, by their sacrifice, the freedom that we enjoy today.
Deputy Lord Mayor Christopher Stalford
"I think it's right that we should pay our respects to those that serve us and who continue to serve us in ongoing conflicts such as Afghanistan," Alderman Stalford commented.
Also in attendance for the second successive year was Tanaiste Eamon Gilmore TD, who also laid a laurel wreath during the service.
"I think it is very important that we commemorate together, the Irish government regards it as very important," he told UTV.
"Over 200,000 people from all over the island of Ireland were in the First World War, many of them lost their lives, and I think it's important that all of us from all parts of the island, including the Irish government, commemorate who died in the wars."
In Ballygawley, Co Tyrone, a church service and wreath-laying ceremony was held for the victims and survivors of the bus bombing in 1988.
Eight soldiers died in an IRA landmine attack on the main Omagh to Ballygawley Road.
Elsewhere, the Queen led the tributes at Whitehall's Cenotaph in London and laid the first wreath in memory of fallen servicemen and women, followed by members of the Royal Family including the Duke of Edinburgh, the Duke and Duchess of Cambridge and Prince Harry.
Prime Minister David Cameron, as well as former leaders Sir John Major, Tony Blair and Gordon Brown also took part in the ceremony - while DUP deputy leader Nigel Dodds represented Northern Ireland.
The poppy was adopted by the Royal British Legion as a fundraiser and symbol of support for those in the Armed Forces. The tradition began two years after the end of the First World War in 1921 and was inspired by the John McCrea poem In Flanders' Fields.