Unlike the award for his hit Just The Way You Are, his brush with the law in Las Vegas may not last forever.
Mars will avoid prison and will have no conviction on his record if he stays out of trouble for a year and meets other conditions of his plea deal.
Clark County District Judge Jessie Walsh made sure Mars understood that he could face up to four years in state prison if he violates the terms of the agreement.
"You understand the penalty range?" she asked.
"Four years," Mars replied, standing in a dark suit with his hands at his sides.
The judge gave Mars - real name is Peter Gene Hernandez - probation, a $US2000 fine, 200 hours of community service at a non-profit organisation and eight hours with a drug counsellor in Los Angeles.
Walsh set a January18 date for Mars to return to court.
His Las Vegas lawyer, Richard Schonfeld, told the judge that Mars intends to meet the requirements.
Mars, who performed at the Grammys and took home the award for best male pop vocal performance for his song, declined to comment in the court hallway.
He acknowledged having 2.6g of cocaine when he was arrested in a bathroom early on September 19 after a nightclub performance at the Hard Rock Hotel & Casino in Las Vegas.
Police say he told the arresting officer he never used drugs before.
Mars' Los Angeles lawyer, Blair Berk, has said the singer appreciated the chance he was getting as a first-time offender to have the felony charge dismissed.
The former child entertainer from Hawaii began his career at age 4 as an Elvis impersonator. He moved to Los Angeles in 2002.
His label, Elektra, announced this week that Mars would headline with recording artist Janelle Monae on a North American tour dubbed "Hooligans in Wondaland."
