Citing reports from Brazilian media organisation Globo Esporte, the report claims Deco will be suspended for 12 months after testing positive for hydrochlorothiazide and cardoxy-tamoxifen following the Fluminense versus Boavista match on March 30, 2013.
But the announcement comes just a month after the Portugal international and ex-Chelsea midfielder confirmed his retirement from the sport.
The illegal substances are believed to aid recovery from injury, but Deco and his defence team insisted they were simply caused by a vitamin tablet.
He was initially banned for 30 days following the positive test in March, but that suspension has now been increased to a full 12 months.
Not that that will affect him too much though, following the 36-year-old's announcement earlier this summer that he was calling time on his career.
The former Stamford Bridge midfielder spent two seasons with Chelsea, before leaving Europe to return to Brazil to play for Fluminense.
A Champions League winner with Porto - under Jose Mourinho - back in 2004 - Deco played professional football for 17 years, winning league titles in four different countries and two continents.