Pjanic has moved to Barca from Juventus as part of a deal that was agreed in June, with Brazil international Arthur going the other way.
While Arthur became an isolated figure thereafter, Pjanic completed the rest of the campaign with Juve and was set to link up with Barca imminently.
[BREAKING NEWS]— FC Barcelona (@FCBarcelona) August 23, 2020
Pjanic tests positive for Covid-19 and will travel to Barcelona in 15 days. Player feeling well and self-isolating pic.twitter.com/sTr9s4pzvc
However, Barca have announced the 30-year-old will now join them in 15 days' time, after he tested positive for COVID-19.
"Pjanic tested positive for COVID-19 on Saturday, August 22 after suffering some discomfort. The player is in good health and is isolated at home," a statement read.
"For this reason, the player will not travel to Barcelona until 15 days later to join Barca."
Pjanic leaves Juve having won four Serie A titles and two Coppa Italia trophies.