He had been in hospital since the incident in Blanchardstown.
Gardaí have launched a second murder investigation following the death of the man who was shot in a restaurant in Dublin on Christmas Eve.
48-year-old Jason Hennessy was pronounced dead at the Mater Hospital today.
His alleged attacker, Tristan Sherry, was stabbed to death during the incident, and three people have been arrested in connection with his death.