The Australian, seeded 14th, is known for his grit and determination and needed it as he claimed a 4-6 3-6 6-2 6-4 6-2 win in almost three-and-a-half hours on the Philippe Chatrier court.
Gaudio, the 2004 champion, looked in control when two sets up but allowed Hewitt to launch a familiar fightback.
After seeing himself pegged back to two sets all, Gaudio trudged back to his seat after being broken in the opening game of the decider.
Hewitt had no further problems and set up a third-round clash with Jarkko Nieminen, but he admitted Gaudio caused him problems early on.
“He was probably one of the toughest second-round matches you can get here,” said the former world number one, who lost to Gaudio during the Argentinian’s run to the title three years ago.
“He was hitting his backhand great, and he wasn’t missing many balls.
“It was a matter of just hanging in there, and just focusing on winning one set at a time.”
Hewitt had a poor 2006 but he has found his form again this year, especially on clay.
He took Rafael Nadal, king of the dirt, all the way in their Hamburg Masters semi-final earlier this month, losing the third set 7-5 in an epic.
Nadal extended his unbeaten run at Roland Garros to 16 matches thanks to Thursday’s run-of-the-mill 6-2 6-1 6-4 victory over Flavio Cipolla.
The Spaniard, who is yet to be defeated here since making his debut in 2005, is bidding to become the first man since Bjorn Borg in 1980 — and the second in 93 years — to win three Roland Garros titles on the trot.
“It’s not a match where I played my best tennis, but I felt good. I’m playing better and better every day,” he said.
Meanwhile Nieminen, seeded 20, thrashed Mathieu Montcourt, of France, 6-1 6-1 6-4 on Court 3.
Cypriot Marcos Baghdatis defeated Denmark’s Kristian Pless 7-5 6-3 6-4 on court one. He will next play Jan Hajek, who beat fellow Czech Bohdan Ulihrach in five sets.
Serbia’s Novak Djokovic, the sixth seed, secured victory over France’s Laurent Recouderc 6-3 3-6 6-3 6-1 while Ivo Ljubicic, seeded seven, joined him in the third round thanks to a 6-4 6-3 6-7 (3/7) 6-3 triumph over Swiss Stanislas Wawrinka.
Spanish duo Carlos Moya and David Ferrer also progressed with comfortable wins against Florent Serra and Diego Hartfield, respectively.
In the women’s competition, Serena Williams admitted there was room for improvement in her game despite sealing a third-round spot with a straight-sets win yesterday.
Williams’ started like a train against Venezuela’s Milagros Sequera before almost coming unstuck in the second set. She ended up triumphing 6-0 7-6 (7-3) to set up a match against Michaella Krajicek.
But she was left feeling there was more to come as she seeks a second Roland Garros singles title to add to the one she won in 2002.
“I honestly did not feel my game at all. Even in the first set, I felt like I was not playing well.
“I was struggling to get rhythm — maybe I had too many days off.
“But I was able to come back and I found more rhythm towards the end.”
Second-seed Maria Sharapova was able to put aside her injury problems to breeze past Jill Craybas 6-2 6-1.
She will now play Alla Kudryavtseva, who prevailed 7-5 1-6 8-6 in an epic with Argentina’s Gisela Dulko.
Seventh-seed Ana Ivanovic, one of two Serbians in the world’s top 10, beat Sania Mirza 6-1 6-4 on court one to set up a third-round match with Ioana Raluca Olaru.