The suspension of Taveras, who is currently on the Nationals' Gulf Coast League team, will be effective at the start of the 2011 season.
Last season, Taveras hit a combined .300 with 24 RBIs for the Gulf Coast Nationals and Class A Hagerstown.
Taveras is the second member of the Nationals organization to receive a suspension in less than a week.
Catcher Adrian Nieto also was handed a 50-game suspension on Thursday after testing positive for Oxandrolone and metabolite.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.