The Cork brothers produced a stirring finish in the lightweight double sculls to overtake the Italians into second but had left themselves too much to do to catch first place Norway.
The 2016 Olympic heroes, who also claimed a silver medal in Rio De Janeiro, clocked a time of 6:22.84, 1.99 seconds behind the Norwegian crew of Are Strandli and Kristoffer Brun.
Gary told RTE Sport afterwards: “It was a tough ould race, we’re feeling pretty shagged now but we’ll recover in time. We gave it a good old go, the Norwegians were just too quick.
“We planned to keep within touching distance of them within the first 500m.
“The plan then was to move through towards the kilometre mark. We gained a lot on the Norwegians but they were just a bit fitter and stronger today.”
— RTÉ Sport (@RTEsport) August 5, 2018
Paul added: “I’m a little but disappointed with silver but we know the Norwegians are pretty good. The main focus for the year now will be the World Championships.
“There’s a lot to do over the next few weeks but that will provide some motivation at least.”
The World Rowing Championships take place next month in Polvdiv, Bulgaria from the 9th to the 16th of September.
The O’Donovan brothers have already won a gold medal at the World Cup regatta in Switzerland earlier this year.