France dominated the scrum in the second half and scored a brilliant try following a superb individual burst from Gael Fickou that resulted in Thomas’ second try.
Guirado scored his sixth international try 10 minutes from time.
The sides are in the same pool at the Rugby World Cup next year in Japan and will face off in their opening game.
“It feels good after what we went through last week, it was not easy to bounce back,” Guirado said. “I’m happy and reassured regarding our team’s spirit.”
Argentina got a break on the first turnover after Maxime Medard dropped the ball at the breakdown. The Pumas launched a quick counterattack, with Ramiro Moyano released down the left by Jeronimo de la Fuente. Moyano sliced past two defenders to touch down between the posts and Nicolas Sanchez converted the try to give Argentina a 7-0 lead.
Argentina went ahead 10-3 after 10 minutes and an exchange of penalties by Serin and Sanchez.
The visitors kept the upper hand as the French were once again their own enemies through poor passing and handling despite some good inspiration. France wasted an excellent chance from its own 22 when Thomas sped down the left flank and opened up a gap only for flanker Wenceslas Laurent to knock on.
The French insisted, and were finally rewarded in the 24th with a well-built try from a quick lineout. Thomas concluded the move after wing Yoann Huget found Fickou on the right flank. The center released Thomas, who crossed in the corner.
The Tricolores took the lead seven minutes before the interval as Serin kicked a penalty after Santiago Medrano was penalized in the scrum.
Argentina won a penalty in the 46th minute after Huget failed to release the ball in a ruck and the visitors went back in front.
But the Pumas ran out of steam and a flash of brilliance from Fickou ignited France. The center collected the ball 35 meters from the line, feinted a pass, and escaped four tackles before offloading to the unmarked Thomas in the right corner.
Serin converted to put France up 18-13.
Center Mathieu Bastareaud won breakdown ball in the 65th to end a dangerous counterattack from the visitors just before Pablo Matera conceded a penalty for putting his hands in a ruck, allowing Serin to kick another penalty.
Guirado made the scoreline comfortable after Tomas Lezana fumbled the ball straight into the path of the France captain, who dived between the posts. France finally had relief.
France welcomes Fiji next weekend, and Argentina goes to Scotland.
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