French President Francois Hollande said the shootings and bombings on Friday were an "act of war" organised by Islamic State militants.
An Irishman who suffered gunshot wounds in one attack has undergone surgery.
Families from both sides of the Irish border prayed at the Irish College chapel.
Among them was Jessica O'Gara, wife of former Irish international rugby player Ronan O'Gara, who is now based in France.
She described the situation in Paris as "frightening".
Fr Dwayne Gavin, the chaplain to the Irish community, said the gunmen involved in Friday's attacks were "cowards".
He described the people who were killed as "martyrs".
Irish ambassador to France Geraldine Byrne also attended the mass.
She said that information to date suggests only one person from Ireland was injured in the attacks.
The man, who had surgery to his wounds on Saturday, had been visiting Paris for the weekend.
It is understood he had been at the Bataclan concert hall, where 89 people were killed when gunmen opened fire inside the venue.
He is in a serious but stable condition in hospital.
Home Secretary Theresa May said concerns remain over a "handful" of Britons caught up in the attacks.
Stepping off a bus at the Arc de Triomphe on Saturday night felt more like Belfast in the 1970s than Paris in the 21st Century.
On one corner was a large group of armed police officers, on the other was a squad of young soldiers.
There was a khaki-green army pick-up truck beside them, looking totally out of place in a part of Paris associated with tourism rather than terrorism.
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What we know about the Paris attacks
A number of people have been arrested in Belgium over the attacks that have left about 350 people injured.
One Briton, Nick Alexander, has been confirmed dead. He was also at the Bataclan.
Former Belfast priest Fr Aidan Troy, who now lives in Paris, said people in the city were offering to do what they could in the wake of the attacks.
He said: "I saw the lines of blood donors who are going to the hospitals and saying: 'You are short of blood, can we give blood?'
"Tourists are going and doing it.
"There has been a tremendous outpouring, almost like saying: 'Evil will not win, good is going to come out on top.'"
Belfast City Hall and other local government buildings in Northern Ireland were lit in the colours of the French national flag on Saturday evening in an act of "solidarity" with the French people.
Books of condolence are being opened at Belfast City Hall and Londonderry's Guildhall.
On Monday, a minute's silence will be held by the Northern Ireland Assembly and the Irish parliament as a mark of respect to the victims.
Members of the Irish community in Paris have united at morning mass to pray for peace, after attacks claimed the lives of at least 129 people.