Paulino, who will be ineligible to play for the remainder of the season, will begin serving his suspension on Friday night, when the Marlins host the Astros at Sun Life Stadium in Miami.
An MLB statement did not reveal which specific drug Paulino tested positive for, but Paulino said it unknowingly stemmed from the use of a dietary supplement. He said he will not challenge the suspension.
"To control my weight this season, I used a dietary pill," Paulino said in a statement released by the Marlins. "Regretfully, I recently learned that the dietary pill contained a substance banned under Major League Baseball's drug policy. I am ashamed and saddened for disappointing and distracting my family, my teammates, the entire Florida Marlins organization and baseball fans. My heartfelt and most sincere apology. "
The last Major Leaguer suspended for testing positive under MLB's Drug Policy was Reds starter Edinson Volquez on April 20. Volquez wound up serving his 50-game suspension while on the disabled list. Prior to Volquez, Dodgers outfielder Manny Ramirez received a 50-game penalty in May 2009.
In his second year with the Marlins, Paulino began the season in a platoon situation with John Baker, then assumed an everyday role when Baker went down with a right flexor muscle strain in May.
Paulino, a native of the Dominican Republic, is batting .259 with four homers and 37 RBIs in 91 games. His batting average stood at .305 as recently as July 2.
The Marlins recalled catcher Brad Davis from Triple-A New Orleans to fill the void on the active roster. Paulino was placed on the restricted list.
"I was irresponsible for failing to take all precautionary steps in confirming the approval of the dietary pill," Paulino said. "Without a doubt, I have learned from my mistake."