The actor was also sentenced to three months probation and must complete 36 hours of domestic violence counseling.
Sheen appeared upbeat in the courtroom. Asked to enter a plea, he told the judge, "Guilty as charged your honor." Asked why he was submitting that plea, Sheen replied, "Because I'm guilty."
The actor added in a statement following the sentencing: "I'm very grateful to the court and to the people of Pitkin County. I look forward to complying with the court's decision, getting on with my life and putting this behind me."
Sheen's lawyer, Yale Galanter, is pleased with the case's outcome, saying, "Charlie got a great sentence, and I am privileged to have been able to do this for him."
The Two and a Half Men star, 44, will be back at work on the set of his hit sitcom Tuesday working on the first episode of the new season.
Previously Sheen had pleaded not guilty to a felony menacing charge and two misdemeanors stemming from the couple's Christmas Day fight, in which Mueller, 32, told police he had pinned her down and threatened her with a knife.
A month after the alleged incident, Mueller entered a "wellness program" before checking into rehab for substance abuse. In February, Sheen also sought treatment at a rehabilitation facility as a "preventative measure," his rep said at the time.
As for the couple's future, Galanter says Mueller and Sheen have a solid bond as parents to their two sons, and hopes they can begin to heal their relationship. "I am not a fortune teller so I can't be sure what will happen between them," Galanter tells PEOPLE. "But Charlie goes back to work tomorrow. He wants to move on with his life in a positive way."
With reporting by LINDA MARX