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.
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