The viable device was made safe near an ATM machine at the Blanchardstown Institute of Technology on Saturday morning.
Army bomb disposal experts were tasked to the scene shortly after 10.30am.
The area was sealed off, while nearby buildings were evacuated.
A Defence Forces spokesman said: "The device was rendered safe in situ remotely without the need for a controlled explosion and was then moved to a secure military location for further technical examination and testing."
He added: "The device has now been confirmed as a viable IED (Improvised Explosive Device) following further testing and its remains will be handed over to the Gardai to assist in their investigations."
The security alert ended after 11.30am.