Having lost their play-off first-leg 2-0 to Ukraine on Friday, the French entered Tuesday's return fixture knowing no side had ever overturned a two-goal deficit to reach the finals.
Efforts from Mamadou Sakho, Karim Benzema and an Oleh Husyev own goal secured a memorable turnaround at the Stade de France and their place at Brazil 2014.
Deschamps' deal was set to expire after next year's World Cup, but he will now remain in charge of his country until UEFA Euro 2016, which will be hosted by France.
After Tuesday's win, French Football Federation president Noel Le Graet told reporters Deschamps' contract would be extended.
"Didier had my full confidence and he will continue with Les Bleus until Euro 2016," Le Graet said at the Stade de France.
Deschamps had been expected to step down if France failed to qualify, but their remarkable turnaround has led to an extension.
'I love my job. I love being able to play this sport. In the end, there’s something addictive in winning for me' Alexia Putellas speaks about what drove her back from an ACL injury to lift the World Cup
Alexia Putellas: "We’re already the only club to have won the men’s and women’s Champions League, so the only thing even more historic to do than that would be to win it in the same season"
