First Minister Peter Robinson, who chaired the talks alongside UUP leader Mike Nesbitt, described it as the "most representative" unionist group to get together in half a century.
In attendance were politicians from the PUP, TUV and UKIP, as well as the Reverend Mervyn Gibson, Winston Irvine from the loyalist North and West Belfast Parades Forum, and members of the Orange Order amongst others.
After the meeting, leaders said the group aims to hit the ground running on Friday with eight working groups to be set up, looking at issues including identity, flags and the economy.
Mr Robinson said they will go out and listen to the concerns of loyalist communities - and added that they are also willing to talk to paramilitaries.
"We will talk to anyone who wants to talk to us about how we can move forward in an exclusively peaceful and democratic manner," said the DUP leader.
This is something that no one has seen for decades in Northern Ireland and I think it gives us immense opportunities to take the unionist community forward in a cohesive group
"Never before have people within the unionist community had the opportunity of all of their representatives, no matter what their viewpoint might be, to be in the one room looking at a common agenda and moving forward in that direction.
"That's the way forward for Northern Ireland and that's the basis upon which we would be talking."
The group was set up following the street violence that has erupted across Northern Ireland during the past number of weeks, in the wake of Belfast City Council's decision to limit the number of days when the Union flag is flown from City Hall.
Mr Nesbitt said a resolution is only possible through inclusive dialogue.
"The lesson of the last 15 years is that the only thing that works, the only thing that sticks, is inclusive dialogue," he explained.
"And I understand the media asking questions about will you be talking to quote unquote 'loyalist paramilitaries' but I think you also understand that people with that sort of past look at what's up here (Parliament Buildings), look at who goes into that (Assembly) chamber to represent republicanism (Sinn Féin) and they see frankly a hypocrisy and they think one side is being picked on while the other's being celebrated."
Orange Order Grand Secretary Drew Nelson and Grand Chaplain Rev Mervyn Gibson, who attended the meeting, said they welcomed the fact work by the Forum will "commence immediately".
"The removal of the Union Flag at Belfast City Hall acted as a catalyst to convert a generation of Unionist fragmentation, and it is deeply encouraging to witness the coalescing of the wider Pro-Union family," they said in a joint statement.
"All strands of Unionism now have a real and tangible vehicle to work together on issues of common concern. We must not miss this opportunity for constructive co-operation."
The PUP welcomed the meeting and said there was a "sense of urgency" from all involved.
Dr John Kyle said: "It was positive to see such a wide range of unionist groups present at the Forum as well as the willingness to engage in difficult discussions around the complex and underlying problems that are related to this issue.
"This initial sense of urgency needs to translate into a longer term commitment and vision for our communities."
However, SDLP leader Dr Alasdair McDonnell said the Unionist Forum is a narrow way of resolving tensions and said there is a better way to deal with the issues discussed on Thursday.
I am concerned that the character of the process the leaders of unionism are pursuing will lead to an uneven conversation.
"This is not a positive way to proceed," he said. "I sincerely hope that members of the Unionist Forum can recognise that the only way to resolve current difficulties is by adopting a broad approach to discussions and pursuing an inclusive process."
Sinn Féin MLA John O'Dowd said unionists talking to other unionists will not promote mutual respect for different national identities.
"There needs to be an open discussion on how people's Irishness and Britishness can be respected and valued," he said.
"Unionism needs to face the reality that the North has changed and will continue to change. Any attempts to hark back to a one-sided past will only sow more confusion among unionists and loyalists."
The Union flag was flown at Belfast City Hall on Wednesday to mark the Duchess of Cambridge's birthday, which is one of 18 designated days.
Belfast remained peaceful that evening, following six consecutive nights of rioting in the east of the city, in which 66 police officers have been injured.
Meanwhile a planned loyalist rally in Dublin against the lowering of the Union flag at Belfast City Hall could be delayed.
Police in the Republic said they have taken part in "positive and constructive" discussions with a representative of Willie Frazer, who has been a prominent member of the Ulster People's Forum.
Mr Frazer was one of the driving forces behind the protest which was due to take place in Dublin on Saturday.
He said: "The Garda want to facilitate this protest and we are prepared to work with them. But they said they need more time."