In Enniskillen, County Fermanagh, Northern Ireland Secretary Chris Heaton-Harris and Taoiseach Leo Varadkar attended a commemoration honoring victims of the 1987 IRA bomb attack at the town's war memorial. This attack claimed 12 lives.
In Belfast, wreaths were laid at the cenotaph at City Hall, and similar ceremonies took place in other cities and towns, including a two-minute silence at 11:00 GMT.
The events were dedicated to remembering servicemen and women from both World Wars and later conflicts. Varadkar's participation continued the tradition of Irish leaders attending the Remembrance Sunday event in Enniskillen.
Heaton-Harris emphasized the significance of the joint commemoration by the British and Irish governments.
Other political leaders, including Democratic Unionist Party leader Sir Jeffrey Donaldson and Ulster Unionist Party leader Doug Beattie, also participated in remembrance services in London and Portadown.
The weekend included various other remembrance activities, such as the Lord Mayor of Belfast participating in a city hall ceremony and a 97-year-old D-Day veteran attending the Armistice Day ceremony in Carrickfergus.
In Londonderry, community members and school pupils created white crosses with poppies in memory of locals killed during World War One.