The 'Manchester by the Sea' star won Best Actor during Sunday's ceremony.
The two were nominated for Best Actor at the Academy Awards.
Affleck began his speech by thanking fellow nominee Denzel Washington.
ET caught up with the actor ahead of Sunday night's Academy Awards.
The 'Manchester by the Sea' star opened up to ET on the Oscars red carpet.
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The director also gushes to ET about the Oscar nominations for Casey Affleck and Michelle Williams.
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The 'Hidden Figures' star and the 'Manchester By the Sea' actor had a good laugh at the awards show.
Affleck opened up to ET at Monday's Live by Night premiere, acknowledging the people he relies on most when the going gets tough.
The 'Live by Night' star opened up to ET about the people he relies on most when the going gets tough.
He also listens to a lot of Radio Disney.
He went on to throw jabs at his younger brother on 'Jimmy Kimmel Live!'
