According to club Clermont Auvergne, Pierre was the worst affected as he suffered "severe cuts" to his hip in an attack during the early hours of Sunday morning, local time.
Pierre, Benjamin Kayser and Aurelien Rougerie were walking back to their hotel when they were attacked by a gang wielding machetes, knives and swords following a night out in the Millau area of southern France.
The club confirmed on Monday that 32-year-old Pierre - capped 27 times by France - had been operated on and would leave hospital later on Monday before resuming training in a month's time.
"Julien Pierre, the player most seriously ill, had surgery late yesterday afternoon to treat his severe cuts," read a statement on Clermont's website.
"The operation was carried out without any complication. He will resume training in about a month."
Club captain Rougerie sustained tendon damage to his neck but was released from hospital last night and will required three to four weeks recovery.
Rougerie has been capped more than 70 times at international level and has returned to Clermont's training camp in Falgos.
Kayser is also likely to require four weeks before he can return to action after he left hospital on Sunday evening.