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.

Local Parents Could Be Hit Hard As Creches Threaten To Close Over Funding Crisis
Five Young People Dead Following Two-Vehicle Crash In Louth
Athy Locals Praised After Elderly Dog Saved Following Dramatic Canal Lock Ordeal
€4.4m Cannabis Seizure Sparks Arrests Across Kildare And Dublin
Survivors’ Stories And Counselling Gave Kildare Woman Maeve Leahy Strength To Speak Out About Abuse
€34.5m Boost Backs Quest To Study Memory Loss And Build 3-D Biodegradable Spinal Supports
13 New Gardaí For Kildare - But No Increase For Part-Time Maynooth Station
Kildare’s Rain Warning Brought Forward To 9am As Remnants Of Storm Claudia Approach Ireland