Northamptonshire Police is appealing for witnesses after the burglary on Friday, November 18.
Sometime between 12.30pm and 2pm, three men broke into a flat in Booth Meadow Court, Thorplands.
They stole a safe, which contained jewellery of “high value,” said a police spokeswoman, before leaving the flats through the rear door.
The offenders are described as wearing balaclavas, around 6ft and dressed in black.
Anyone with information can contact Northamptonshire Police on 101 or Crimestoppers anonymously on 0800 555 111.