This time they were stolen from west-end apartment parking lots, police said in a news release on Wednesday.
Two catalytic converters were stolen on Silvercreek Parkway North, while another was removed from a vehicle at a Westwood Road apartment building.
Police said there have been more than 40 such thefts in the city since Christmas.
Drivers are encouraged to park in public well-lit areas when possible and to report suspicious activity, especially during overnight hours in areas where vehicles are left unattended.
Anyone with information about catalytic converter thefts is asked to call police at 519-824-1212 ext. 7336.