It happened at 12:41 a.m. on Monday in the 1300 block of Germantown Avenue.
Investigators say the victim was approached by an unknown man, who started talking to him.
During the conversation, police say the suspect pulled a gun, placed a knife to the victim's throat and ordered him out of the vehicle.
That's when the suspect stole the victim's 2001 Lexus RX 300 SUV.
Police say the suspect may have been the passenger in a four-door white sedan that was seen in the area.
The person police are looking for is described as a Hispanic man, about 35 years old with short black hair. He was wearing a white t-shirt and blue jean shorts.
Anyone with information is asked to contact Philadelphia Police at 215-686-TIPS (8477), text a tip to PPD TIP (773847) or through PhillyPolice.com.