Michael Green, 30, of Glenside, Montgomery County and Julian Collins, 22, of Philadelphia were arrested for the incidents on Wednesday night.
Police say Green was one of two men in a Chevy Malibu who made a traffic stop in the 4300 block of McMenamy Street.
Investigators say they made the stop while flashing red and blue emergency lights.
"One of the guys had a shirt with the word 'police' written on it," said Philadelphia Police Lieutenant John Stamford told Action News on Thursday. "It's not an official police shirt."
Stamford said both suspects were armed with guns when they forced three victims out of their Chevy Silverado, handcuffed them, pushed them back into the truck and drove off with the victims in the back seat.
The suspects stole two of their cell phones. After a struggle, the victims somehow escaped. Police later found the would-be hostages still handcuffed. One suffered a broken arm.
The suspects' Chevy Malibu was later recovered at Hartell and Walker Streets.
The second suspect in this case remains at large.
Within the hour on the same night, Philadelphia Police stumbled across a second police impersonator in the same area.
Police tell Action News a victim pulled into a 7-Eleven parking lot on the 9000 block of Frankford Avenue and was followed by a suspect driving a Toyota Camry. The Camry was flashing a strobe light, and the suspect identified himself as a police officer.
"While this was taking place," said Stamford, "two Philadelphia Police officers in the area observed this incident taking place."
The suspect, Julian Collins, was arrested at the scene.
Police tell Action News the two incidents do not appear related. They are advising people that if you're pulled over by an unmarked vehicle, take precautions.
"Do not hesitate to call 911," said Stamford. "Give a location of where you are, a description of the person stopping you, and tell 911 dispatchers that you're requesting marked unit."