Police reported Military Road was closed in both directions between Privett Road and Station Road at around 10.30am following the discovery on HMS Sultan.
People were warned to avoid the area as Gosport police led the operation.
A post by the authority on Twitter said: ‘Please avoid the area. We will keep you updated and let you know as soon as the road has reopened.’
But a subsequent post by police revealed the road had been reopened after revealing the device was different to what was first expected.
‘Military Road has now reopened. Thank you for your patience. The Royal Navy EOD team has attended and established the suspected unexploded ordnance was not as first thought,’ the post said.
Travel service Romanse said there were no delays in the area following the incident.