The Hangover 2 actor admitted that his addiction to alcohol was affecting his career.
"It just got to a point where it was like, 'You know what? I've got to stop'," he told The Sunday Mirror.
Cooper added: "It was just the kind of thing where if I wanted to continue to live."
The 37-year-old is reportedly in a relationship with Star Trek actress Zoe Saldana.
The star was named 'Sexiest Man Alive' by People magazine in November last year.
Watch Bradley Cooper talking to Digital Spy about the Hangover series below: