Giroud featured for the full 90 minutes in France's 1-1 draw with Paraguay in Nice, in which both sides traded goals in the final eight minutes.
The Arsenal front-man revealed Ribery was feeling frustrated by his layoff due to chronic pain in his lower back.
The Bayern Munich man was not seen for their friendly with the Paraguayans, and Giroud said Ribery was increasingly concerned, with their World Cup opener against Honduras on June 15 growing nearer.
"He began to be angry," Giroud said, as reported by l'Equipe .
"I do not know if true, but he is worried and concerned about his situation."
He added: "We must help him hold on and be patient. When I'm injured for three days, I lose it. It is on the eve of the World Cup."
France coach Didier Deschamps was tight-lipped so as to not fuel speculation on Ribery's availability for Brazil, conceding there was 'nothing new' to add following the Paraguay match.
Loic Remy, who was deployed on the left in Ribery's absence, said France's missed opportunities early in the fixture at the Allianz Riviera cost them a result.
"We started very well, we had a lot of opportunities we did not know and realize in the end, it gets punished after opening the scoring," Remy said.
"This kind of meeting should enable us to rectify before the World Cup . We must be vigilant and not concede a goal in that way."
