Mars, whose real name is Peter Hernandez, and his lawyers agreed not to contest police accounts that he possessed 2.6 grams of cocaine when he was arrested last September.
Las Vegas Justice of the Peace Joseph Sciscento set the Feb. 14 date for his plea - the day after the 53rd Grammy Awards show in Los Angeles.
Under the plea deal, the pop star will spend a year on probation, pay a $2,000 fine, perform 200 hours of community service and complete drug counseling.
Mars was arrested on Sept. 19 in a casino restroom after a nightclub performance at the Hard Rock Hotel & Casino. Police said he handed over a bag containing 2.6 grams of cocaine, and told the arresting officer he'd never used drugs before.
The Associated Press contributed to this report.