Cleaning up is being carried out at the scene, with damage caused to both the bank premises and ATM.
Police and members of the Northern Ireland Fire & Rescue Service attended the scene shortly before 8.40pm after reports that a man had poured a liquid on the front of the building and set it on fire.
There were no reports of anyone inside the premises.
A 54-year-old man was subsequently arrested on suspicion of arson endangering life with intent, possessing offensive weapon in public place and possessing article with intent to damage property.
Local public representatives have paid tribute to the emergency services for their actions at the scene.
Among those who voiced their appreciation was Sinn Fein Councillor Paul Duffy, who said: “I would like to praise the quick actions of the NI Fire and Rescue Service and the PSNI following this reckless arson attack at the Halifax in Portadown on Tuesday night. It is lucky no one was hurt."
DUP Upper Bann MLA Jonathan Buckley was in the town on Tuesday night shortly after the incident happened.
"I would like to praise the firefighters and the police for their service,” he added.
9. Halifax fire
Some of the damage caused to the Halifax and ATM in Portadown on Tuesday night. Photo: Press Eye
10. Halifax fire
The scene after the fire at the Halifax branch on the corner of High Street and Woodhouse Street, Portadown Photo: Press Eye