The pensioner was shopping in the Aldi on Towngate when two people approached her.
Officers say the lady's bag was on her trolley when an offender reached in and took her purse.
A police spokesman said: "We're asking for your help to trace the man in the CCTV after an 85-year-old woman had her purse stolen.
"The woman was doing her shopping in Aldi when two people approached her. Her bag was on her trolley and, at an opportune moment, one of them reached in and took her purse which had around Â£20 cash inside plus a bus pass and her bank card.
"We believe the card has gone on to be used at various shops in Leyland.
"We think the man in the CCTV still will have important information which could help us with our investigation."
Anyone with information is asked to e-mail police at [email protected]