Thefts have been reported from vehicles parked in Batesquire, Sothall and Birley Spa Lane, Birley.
A window was smashed to get into one vehicle and the lock was forced on the other.
A South Yorkshire Police spokesman said: "Please ensure valuables are removed from vehicles when left unattended and that they are parked on driveways or in well lit areas where possible.
"If you own a van and have another vehicle on your driveway consider parking close to the van doors to prevent offenders being able to open them."
Anyone with information should call South Yorkshire Police on 101.