The 25-year-old Austrian national was detained in his flat in the quaint northern town of Braunau am Inn where the Fuehrer was born on April 20, 1889.
The man, who reportedly called himself "Harald Hitler", was arrested under a 1947 Austrian law which made it illegal to promote Nazi ideology.
"It was obvious that he glorified Hitler," police spokesman David Furtner told AFP.
Images of the man have been posted on Facebook. Photo: Screenshot Servus TV
Authorities became aware of his existence after photos emerged on social media of the man posing outside Hitler's actual birth house, a large yellow corner house in the town's historic centre.
Other snaps showed him standing in a Braunau pub dressed in traditional garb including a loden jacket and lederhosen.
According to local media reports, the copycat introduced himself to patrons as "Harald Hitler" and insisted on being served "Austrian mineral water".
The suspect who offered no resistance during his arrest had moved to Braunau in mid-January, police said.
The case once again puts the spotlight on Braunau, a town of 17,000 on the German border which has repeatedly made headlines because of its historical ties to Hitler.
Most recently it drew attention after the government in December expropriated the dilapidated building where Hitler came into the world.
The move followed years of bitter wrangling with owner Gerlinde Pommer who had been renting the premises to the interior ministry since the 1970s and refused to sell or carry out essential renovation works.
The government said the seizure had been necessary to stop the building from becoming a pilgrimage site for Nazi sympathisers.
In response, Pommer launched proceedings against the expropriation last month, arguing it was unconstitutional.
The court is yet to rule on the case.