The suspension took effect on Monday and will run through July 22.
Oviedo, formerly known as Leo Nunez, reported to the Marlins' complex in Jupiter, Fla., on Monday after spending nearly eight months in the Dominican Republic dealing with legal issues relating to his identity.
On Friday, Oviedo was granted a visa to return to the United States. He took a physical on Monday in Jupiter.
The suspension was expected.
According to MLB, Oviedo is eligible to participate in extended spring camp during the period of his suspension. In addition, during that period, Oviedo will be eligible for one rehabilitation assignment to a Minor League affiliate not to exceed 16 days.
Late last September, Oviedo was placed on the restricted list. He returned to the Dominican Republic to resolve the issues relating to his identity.
Oviedo was the Marlins' closer from 2009-11 and collected 92 saves in 117 chances.
The right-hander had 36 saves in 42 opportunities last season before being placed on the restricted list.
Oviedo signed a one-year, $6 million deal with the Marlins in the offseason, avoiding arbitration. But he will receive only a prorated portion of the salary because the team isn't obligated to pay him until he is cleared to play.