Police say the man, 51, was arrested on Saturday night at 10 p.m. on Quickfall Drive, a small street lined with 1960s-era family homes in Waterloo's Weber Street North and University Avenue area.
"We became aware of it because a lady called and said that this man was outside drinking and acting strangely and wearing a uniform," Waterloo Regional Police spokesman Olaf Heinzel said Monday.
He said the woman did the right thing by calling the local police station.
"You see a person wearing a police uniform openly drinking beer, you might wonder, 'What is this person doing? Why is this happening?' It's not something you'd normally expect a police officer to be doing," Heinzel said.
Heinzel said that once officers arrived, they questioned the man and found he had no affiliation to any police service and was wearing a vintage Waterloo Regional Police service uniform.
"It was our older-style uniform with really old patches, like our former crest," Heinzel said. "He used a jacket that had the old crest on it and a hat with no badge."
The man was charged with impersonating a police officer and public drunkenness.