Braun, the 2011 NL MVP, accepted a season-ending 65-game suspension last week after admitting to making "some mistakes" and apologizing to anyone he may have disappointed.
Braun tested positive for elevated testosterone in October 2011 but a 50-game suspension was overturned the following February by an arbitrator who ruled Braun's urine sample was handled improperly.
Espn.com first reported that Nike had dropped Braun.
Braun wore Nike gear and the company sold T-shirts with slogans including "Braun owns Milwaukee" on them.
Nike, which spends millions on endorsements every year, permanently dropped its personal sponsorship of cyclist Lance Armstrong last October in the wake of allegations that he used performance enchancing drugs.
Beaverton, Ore.-based Nike has distanced itself from other scandal-rocked sports stars before and then taken them back once the scandal faded, however.
It dropped football player Michael Vick, now a Philadelphia Eagle, in August 2007 after he filed a plea agreement admitting his involvement in a dogfighting ring. But it re-signed him in July 2011.
It stuck by the Los Angeles Lakers basketball player Kobe Bryant in 2003 after he was arrested on sexual assault charges that were later dropped. Nike, however, didn't use the basketball player in advertising again until 2005.