Investigators say the suspects are using fake badges and police-style radios to get into homes.
There have been three reports of the police impersonators this past weekend in the city's Albany Park and Jefferson Park communities.
Police say the suspects were not dressed in police uniforms. They were wearing baseball caps and sweatshirts, and some said that they were undercover. In two of the three incidents, an elderly resident was targeted.
"It's disconcerting. It's really disgusting, actually, that people would do that," said Northwest Side resident Jamal Leki.
Residents like Leki are a bit more reluctant to answer their door.
Police have issued a community alert following three separate incidents on three Northwest Side blocks involving men knocking on doors and posing as police officers.
"We are worried about that," said neighborhood resident Mike Blackstone. "But, until something like this happens, we're worried less. And now we have to be worried more."
In two of the incidents the men gained entry into the homes, though it is unclear if anything was stolen.
At one house in the 5000-block of West Gunnison, a suspect reportedly came inside without knocking, claiming to be an officer who saw someone committing a burglary in the garage. He fled with others when a relative of the elderly resident became suspicious.
"I guess we have to be increasingly vigilant that we have to ask for identification," said Blackstone. "It's hard to do though sometimes because you can't see them through the door."
"How do I know you're a real police officer? It's a sticky area. I don't know exactly what I would do," Leki said.
Police say officers are required to show their five-point star badges and city ID cards upon request.
In all three incidents, the men had fake gold badges and police-style radios. They may have been driving a large, dark red SUV or a navy blue Town and Country van.
"Some older people live here and they don't check for IDs ," said Northwest Side resident Steve Alexiadis. "It's kind of dangerous. I hope something's gonna happen to catch these guys."
Alexiadis lives on the same block on North Karlov, where one of the incidents occurred. He says his and other neighbors' homes have been robbed in recent months and wonders if these latest incidents are connected.
"Every day something new comes up. With this high unemployment, people are turning to break-ins and robberies," said Alexiadis.
Police have only a vague description of the suspects.
Some neighbors ABC 7 spoke with said there have been other instances recently involving people posing as contractors to get into homes. It is unclear if those reports are connected.