Northamptonshire Police has released CCTV images of two people they want to speak to in connection with the theft in St James last week.
Between 10.30am and 10.50am on Monday, June 27, two men approached a woman who was using the NatWest cash machine in St James Road.
They distracted the woman then, after observing her PIN number being entered, removed her card.
They later went on to withdraw £500 from another machine nearby.
Officers would like to speak to the two men pictured, who were wearing jogging bottoms.
Anyone with information or who recognises the men can contact Northamptonshire police on 101 or Crimestoppers anonymously on 0800 555 111.