The Niagara Regional Police says the probe, which was launched in the fall of 2011 with the Ontario Provincial Police, found no evidence of any criminal offences by anyone within or associated with the commission.
The commission's troubles began in 2009 after it came under fire for renewing a contract with the tourist ferry company, Maid of the Mist, for 25 years without considering proposals from competitors.
In November 2010, four executives were fired as the government began their investigation into the commission's spending practices.
It found that one of the executives had racked up $400,000 on his corporate credit card over four years, including a $10,000 hotel bill in England and a $1,800 nightclub tab.
In July, several audits found that staff at the commission often broke rules in filing their expenses, including claiming alcohol when it was not allowed and approving their own credit card bills.