New €60 million ($98.1 million) signing Pjanic tested positive for COVID-19 in August and had to go into quarantine, meaning he only arrived in Barcelona on Friday (AEST).
He worked out at the club's training ground for the first time on Sunday (AEST), ahead of Barca's friendly against Gimnastic.
Barcelona posted photos of Pjanic and Jean-Clair Todibo, who has also been kept away from the team after a positive coronavirus test, being put through their paces.
Alongside the images, the club wrote: "[Pjanic] and [Todibo] have received the medical green light after recovering from COVID-19, and have already trained at the Ciutat Esportiva."
Pjanic was not included in a 25-man squad named by Ronald Koeman to face Nastic, but Lionel Messi was selected.
Messi only started training with his team-mates this week after failing to push through a departure from Camp Nou.
Ousmane Dembele could make his return from injury in the friendly, while maiden first-team appearances could be on the cards for new arrivals Francisco Trincao and Pedri.
Ansu Fati will not take part in the match after sustaining a right hip bruise in training on Saturday (AEST), while Luis Suarez and Arturo Vidal, who are reportedly nearing respective moves to Juventus and Inter Milan, were also left out.