GARDAI investigating the murder of Dean Johnston in Clondalkin last year have arrested a 23-year-old man.
He was detained yesterday evening in Co Wexford.
He is being held at Lucan Garda Station under Section 50 of the Criminal Justice Act 2007, a Garda spokesman said.
The 20-year-old was shot dead near his home in Moorfield Avenue, Clondalkin, on May 25 , 2011.
A number of people, including a 36-year-old woman, have previously been arrested and questioned about the killing.