The hospital, which takes patients from the Shropshire border, went into complete lockdown on Thursday after reports of a suspicious package left on the site.
People, including those in ambulances and women in labour were turned away and staff and patients inside were told not to leave their wards. Roads around the Croesnewydd site were closed off and a massive emergency services operation was launched.
The hospital was re-opened in the late afternoon with North Wales police saying the incident had been sparked by a bomb hoax.
Today Detective Inspector Andrew Gibson said police had arrested a man following the incident at Wrexham Maelor Hospital.
He said: “The 33-year-old is local to the area. It’s not possible to provide further details at present - but there are no wider public safety concerns."