Armed gardai fired a shot during a stand-off with a man with a replica gun.
A probe is under way following the incident, which happened in the early hours of this morning when officers were called to Greencastle Road, Coolock.
Gardai said the man, who was aged in his 20s, threatened officers and members of the public.
An armed response team was drafted in and one shot was discharged by a Garda.
"The area was sealed off and following a stand-off a male was arrested," said a Garda spokesman.
"A replica firearm was recovered by gardai at the scene.
"There was no one injured."
An Garda Siochana Ombudsman Commission (GSOC) has been notified and an investigation is ongoing.
The suspect is being detained under Section 30 of the Offences against the State Act, 1939, at Coolock Garda Station.
The scene is preserved for a technical examination.