Fiat, which held a 25% interest in Chrysler, has increased that to 30%, the company announced on April 12.
It is the second time this year that Fiat has increased its ownership in the U.S. automaker. It was originally handed a 20% stake in Chrysler as part of the company's 2009 bankruptcy reorganization. In January the stake was increased to 25%.
Fiat chief Sergio Marchionne, who also heads up the U.S. auto company, said in January that Fiat may boost its holding to 51% before a planned share offer by the Chrysler Group at the end of this year.
The Chrysler group underwent a government-supported bankruptcy reorganization in 2009. It reported a net loss of $652 million last year.
If Fiat increases its ownership of Chrysler to 51% that would help the U.S. government wind down its 8% stake in the smallest of the U.S. Big Three automakers.
The latest increase slightly reduces the stake of Chrysler's other owners. The United Auto Workers health trust, known as the Voluntary Employees' Beneficiary Association, remains the largest shareholder, with 59.2%, followed by Fiat then the U.S. Treasury's 8.6%. The Canadian government holds 2.2%.
The union trust and governments intend to sell their stakes once Chrysler goes public in 2012.