The 21-year-old Fekir, whose father is Algerian, has been in the spotlight in the French media in recent weeks after initially pledging his international future to Algeria before changing his mind.
"Fekir's choice is firm and definitive," Deschamps said. "He's made it clear."
He has been one of the best players of the season and has helped Lyon, which relies heavily on homegrown players like Fekir, to first place in the French league ahead of big-spending Paris Saint-Germain.
The highly-skilled Fekir has scored 11 league goals and a set up a further seven this season.
"He has a lot of potential, he's versatile and he can bring us something different," Deschamps said. "His game is varied, with the way he controls the ball and accelerates."
Deschamps also called up 20-year-old Chelsea defender Kurt Zouma.
France plays Brazil on March 26 and Denmark three days later.
Manchester City defender Eliqauim Mangala loses his place after a recent loss of form, but club teammate Bacary Sagna returns.
France, which is already qualified for next year's European Championship as host, has only friendlies to play in until the tournament.
The French Football Federation will honor France's all-time leading scorer Thierry Henry before the Brazil match at Stade de France, along with former midfielder Patrick Vieira and center-back Marcel Desailly.
They all played more than 100 times for France and helped Les Bleus win the 1998 World Cup and Euro 2000.
Defenders: Patrice Evra (Juventus), Christophe Jallet (Lyon), Laurent Koscielny (Arsenal), Bacary Sagna (Manchester City), Mamadou Sakho (Liverpool), Benoit Tremoulinas (Sevilla), Raphael Varane (Real Madrid), Kurt Zouma (Chelsea)