Thieves stole a jacket and a mobile phone from a Peugeot 106, which had been left in the car park of Glossop Leisure Centre, in High Street East.
The break-in occurred overnight between Sunday and Monday, September 22 and 23.
Police are appealing for witnesses to call 101 and are reminding drivers to remove valuables from their cars whenever they leave them unattended.
PC Matthew Cox said: “It only takes a few seconds for a thief to break in to a vehicle and steal something they can see has been left inside.
“It also only takes a few seconds to pick up valuables and take them with you, which can prevent your car being targeted in the first place.
“Thieves often only strike when they think it is worth it, so taking your items with you or removing them from view can put them off and save you a lot of hassle, distress and cost.”