South Yorkshire Police said the force has noticed an increase in thefts over recent months.
Catalytic converters, which convert exhaust gases into less toxic substances, are valuable to thieves because of their scrap metal value.
South Yorkshire Police is urging people to be on the look out for people appearing to be ‘working’ on vehicles in car parks or on the streets.
The force said: “We are working to apprehend those responsible and have increased patrols and activity around this.
“You are able to help us prevent these thefts by protecting your vehicle with some simple steps.
“If possible, park your vehicle in a locked garage or under well-lit area.
“Install an alarm to your vehicle, particularly ones that activate when a vehicle is tilted or lifted.
“Consider using a catalytic converter protection device or marking system.”
The force added: “Be aware of persons appearing to be working on vehicles in local car parks or on the street.
“Report any suspicious behaviour to the police via 101, or if necessary 999.”