The Berlin-based watchdog said in a statement the task force driving the investigation known as "Operation Car Wash" was receiving the award today during the 17th International Anti-Corruption Conference in Panama City.
Since 2014, the task force has been probing charges of corruption and money laundering at Petrobras.
Dozens of executives and politicians have been arrested or are being investigated for allegedly overcharging contracts with Petrobras and using part of the money to pay for bribes and electoral campaigns.