New Les Bleus coach Marc Lievremont revealed on Friday that the Castres lock would be taking the armband from Raphael Ibanez, who quit international rugby on Thursday.
Nallet, 31, has never been a regular in his national team and only played a peripheral part in their run to the World Cup semi-finals last year.
But Lievremont has chosen the second-row forward as the man to lead France into the forthcoming RBS 6 Nations Championship - and ultimately into the 2011 World Cup.
Nallet, who has accumulated 32 caps, said: "It was a massive surprise. Then I realised it was a great honour that had been handed to me, especially coming from Marc, who I appreciated when he was a player.
"I can't wait to get going - I want to enjoy myself and win titles. To start off with, the Six Nations that is coming up," he said in an interview with French daily L'Equipe.
With the likes of Ibanez, Fabien Pelous and Christophe Dominici all retiring, and the possibility that fellow veterans Serge Betsen and Pieter De Villiers could join them, the experienced heart of the France team is being ripped out.
Nallet has the task of helping bring the new breed of French stars through to the international scene. His first game as captain should come at the start of February when France play Scotland at Murrayfield in the first round of fixtures in the 2008 Six Nations.