Ajaccio will hope that Zubar, who has played more than 100 games in Ligue 1 with Caen and Marseille, can prove an adequate replacement for Medjani as they continue to hover just above the relegation zone in 15th place, just two points clear.
"It is now official that Ronald Zubar will join ACA tomorrow," a statement said on the club's website.
"The central defender, 27, spent the last three and a half years in England with Wolverhampton. He played more than 50 games in the Premier League."
Zubar earned 15 caps for France Under-21s between 2004 and 2007 - a period that coincided with Medjani captaining the side.
Medjani, who joined Ajaccio from Lorient in 2008 after beginning his professional career with Liverpool, drops down a division to join Monaco but will hope for a swift return to the top flight with the principality club level with Nantes at the top of the Ligue 2 standings.
Ajaccio president Alain Orsoni thanked Medjani for his contribution.
He said: "The player gave the best of himself during six years wearing our colours. It was difficult to (deny him the move) after all he has done for the club."
Ajaccio also confirmed that Karim El Hany has moved on, joining FC Brussels after scoring two goals in 32 appearances.
Meanwhile, defender Steven Mouyokolo has had his contract cancelled by mutual consent.