Llodra next will meet eighth seed Max Mirnyi of Belarus, who got past Thailand's Paradorn Srichaphan, 7-6 (7-3), 6-4.
Wednesday evening's second-round contests found fourth seed Andy Roddick taking on fellow-American and wild card Brian Vahaly. Also, No. 7 Xavier Malisse of Belgium faced another American, Taylor Dent.
Llodra needed almost two hours to win his first career meeting with Grosjean. Ranked 101st entering this week, he recorded the biggest victory of his career, beating the player ranked 11th in the world.
"Today I think I'm not going to play against a French player, I tried to pretend I was playing someone else," Llodra said. "I tried to stay focused and play my best tennis."
Grosjean traditionally struggles against his fellow countrymen. There are four other French players in the top 50 -- No. 36 Arnaud Clement, No. 38 Fabrice Santoro, No. 41 Nicolas Escude and No. 48 Julien Boutter -- and Grosjean has posted a 5-14 record all-time against them.
"Sometimes you play against a Frenchman and you are French, the tennis is very bad," Llodra said. "But today it was OK."
The 22-year-old Llodra won five of the first seven points in the third-set tiebreaker. On triple match point, Grosjean fired a running forehand long.
Mirnyi has reached a pair of semifinals in 2002. He made the last four at the Sydney hardcourt event in January and the Hamburg claycourt tournament in May.