The new film from the Cannes favourite, set in the 1930s, stars Kristen Stewart, Jesse Eisenberg, Steve Carell and Blake Lively.
Allen, who was joined by cast members Stewart, Eisenberg and Lively on the red carpet, was making his 12th Cannes appearance.
It was his third time opening the international fest. "Cafe Society," a fairy tale set in 1930s Hollywood, made for an appropriate launch to a festival that focuses on classic movie glamour.
The film festival, however, got off to an awkward start when Allen, was the subject of a rape joke during the opening ceremony.
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"It's very nice that you have been shooting so many movies in Europe, even if you are not being convicted for rape in the US," said master of ceremonies Laurent Lafitte.
The joke, which drew gasps from the Palais audience, was taken as a knock on Allen and possibly on director Roman Polanski as well.
Lafitte also made a touching statement about the Paris attacks. "Since the attacks in Paris, we have been told we are at war. It will take a Gus Van Sant with Elephant or a Roberto Benigni with Life Is Beautiful to help us understand and move forward ... We are waiting for ours ... This is what cinema does," he said.
Before the opening ceremony, the red carpet was damp with rain before sunshine and stars like Justin Timberlake warmed up the atmosphere.
Oscar-nominated actress Jessica Chastain was also on hand for the festivities, and so were Eva Longoria, Victoria Beckham and Naomi Watts.
Timberlake was in France to promote his new animated film "Trolls" opposite Anna Kendrick, who wore a stunning yellow gown.