The four international banks had been charged for allegedly helping the Italian food group mislead investors.
An Italian prosecutor had asked earlier this year that they should be fined and that about 120 million euros ($173.5 million) of their profit should be impounded.
The four banks had repeatedly denied any wrongdoing.
Parmalat, known for its long-life milk, buckled in December 2003 under a 14 billion euro hole in its accounts. Its demise wiped out the savings of more than 100,000 retail investors who had bought the group's investment-grade corporate bonds.
(Reporting by Manuela D'Alessandro, Writing by Lisa Jucca)