The incident happened early Thursday at about 12:30 a.m. near the 5700 block of Thousand Oaks Circle in northwest Houston.
Police said the man came outside and observed a group of men possibly trying to steal the catalytic converter from his pickup truck.
As the man went to confront them, a suspect came out from under the victim's truck and shot him in the chest, HPD said.
According to HPD Lt. Izaguirre, the suspects then fled in a gray Dodge Charger.
First responders transported the victim to a local hospital and said he's expected to survive.
Houston police said there's been a string of catalytic converter thefts in the area. A description of the suspects has not been released.
The investigation is ongoing.