Lincolnshire Police is urging residents, particularly in Lincoln, to ensure their car is locked and valuables removed over the festive period.
The warning comes after two thefts from cars in the city in the past three days.
The first happened overnight on December 16-17 on Charles Street, where a car window was smashed and an iPod stolen.
The night after on Lawrence Close, another car window was smashed, and a sat nav and mobile phone were taken during the incident.
Officers state that these types of crimes increase during the Christmas period, so are urging people not to leave presents or other property in their cars.
It only takes thieves seconds to break into a car and steal items.
To give information on either of these incidents, or on vehicle crime, contact Lincolnshire Police on 101.