The Bosnian, a recent arrival from Juventus, will not be able to join his team-mates for pre-season until September 7, with the next La Liga season poised to start five days later.
"Miralem Pjanic has tested positive in a PCR (polymerise chain reaction) taken on Saturday, 22 August after feeling a little unwell," said Barcelona in a statement.
"The player is in good health and is self-isolating at home."
Pjanic is the third Barcelona player to contract the virus, after Jean-Clair Todibo and Samuel Umtiti.
