Gardaí say this latest suspect is being held at a Garda station in west Dublin.
A third arrest has been made in connection with the death of a man at a restaurant in West Dublin on Christmas eve.
Tristan Sherry died during a botched shooting after he walked into Browne's Steakhouse on the main street in Blanchardstown on Christmas eve and shot a man.
He was then tackled and stabbed as he tried to escape.
He was pronounced dead at the scene.
Last Saturday, 22-year-old Michael Andrecut, with an address at Sheephill Avenue in Dublin 15, was charged with his murder.
Yesterday Gardaí detained a second person in connection with Mr. Sherry's death.
He is still being questioned.
Now a third arrest has been made.
Gardaí say this latest suspect is being held at a Garda station in west Dublin.