The most expensive English player did not play against Bulgaria in the Euro 2012 qualifier that England won 3-0 on Friday but has been training well and could play a role against Wales at Wembley on Tuesday.
"His style of life is a problem, if it is not good," Capello told a news conference when asked about the 22-year-old.
"He needs to be careful because he is an important player not only for the England team but also for Liverpool," Capello told a news conference. "I think he understands what he needs to do."
Carroll, who moved to Liverpool last January for 35 million pounds, won his first England cap last November when Capello also urged him to get a grip on his private life.
He was fined last October for assaulting a man in a nightclub and has also been in the media spotlight for his drinking habits, with Capello talking to him about that last year already.
"I think if he wants to be a good player and a good sportsman, he needs to drink less than the normal," said Capello.
"It's a private message," he added when asked what he had told the player. "I spoke with him and it was a private discussion.
"He understands a lot, he is young and we need to help him and speak with him because he is a really important player."
