Gardai investigating the paramilitary display at the funeral of Real IRA faction leader Alan Ryan on September 8 were last night questioning a man in his 30s.
The suspect was detained on Tuesday night and taken to Raheny garda station.
He can be held without charge for up to three days.
The arrest is part of a major investigation by gardai into shots fired outside the Ryan home at Grange Abbey Drive in Donaghmede, on the northside of Dublin.
Gardai subsequently launched a crackdown on dissident republicans and, in particular, suspected members of the Real IRA. The large crowd at the funeral included sympathisers from Northern Ireland.