Caribineri in Venice arrested and charged the man, a 46-year-old thought to be from Israel, after he reportedly shut the currency exchange employee in her office.
He had tried to exchange $100 into euros but became angry over the rate offered, local media reported.
He then tried to cancel the transaction before closing the shutters and allegedly preventing the woman from leaving the office, near the Rialto Bridge.
The woman was reportedly left “upset and frightened” by the ordeal, which lasted around half an hour.
She managed to call local caribinieri, who opened the shutters and arrested the man.
He did not get his money back, according to Italian media reports.
This is the latest in a long series of incidents involving visitors to the lagoon city. In one shocking incident last month, a gondolier was headbutted by a tourist in a row over selfies.
Meanwhile other visitors to the city have found themselves in trouble with police after breaking local rules on “decorum”, including two German tourists who were fined €950 and told to leave after brewing their own coffee next to the Rialto Bridge.
The relationship between Venice and its visitors is often strained, with the city's economy dependent on tourism but its residents increasingly frustrated with the crowding and disruption that comes of hosting 12 million tourists per year.
Authorities have introduced swathes of ordinances to regulate public behaviour, cracking down on everything from snacking in public to wheeling trolley suitcases to failing to wear a shirt.
But many criticize the government for failing to regulate those profiting from mass tourism, especially the cruise ship companies that ferry thousands of people into the historic centre at once.