The vicious burglary happened at an address in the Slieveshan Park area of Kilkeel.
Investigating officer Detective Constable Skillen said: “We received a report that two or three men entered the house of an elderly man sometime around midnight on Tuesday night.
“Once inside, the men tied up the resident, assaulted him and then covered his head with a pillowcase before proceeding to ransack the house moving through several rooms looking through drawers and cupboards.
“The men stayed in the house for around 30 minutes and left the resident tied up in his bedroom when they left the property.
“He managed to free himself and raise the alarm through a neighbour.
“It is believed a sum of money has been taken at this time and the resident suffered facial and head injuries.
“An investigation into this incident is ongoing.
“I would appeal to anyone who noticed any suspicious activity in or around the area of Slieveshan Park on Tuesday evening to contact detectives in Ardmore on 101 quoting reference number 43 29/03/17.
“Information can also be given anonymously through the independent charity Crimestoppers on 0800 555 111.”