The incident happened in Kenilworth Place, off the lower Newtownards Road, shortly after 8.30pm on Wednesday.
No one was in the house at the time and there are no reports of any injuries.
The device, initially described as a suspected pipe bomb, was taken away for further examinations by army bomb experts.
Police said the motive behind the incident remains under investigation.
Residents who were evacuated to a nearby community centre for a time have now been allowed to return home.
Anyone with more information has been asked to come forward.