Luis Enrique's men are set to take on the French champions at the Parc des Princes in their second match in Group E.
But they will have to manage without Douglas, who was forced to withdraw on Monday due to foot injury.
"Martin Montoya is the latest addition to the squad for the Champions League match in Paris," a statement on the club's official website read.
"He takes the place of Douglas, who has a bruised left foot.
"According to the statement of Medical Services, the Brazilian was hurt during training yesterday and this morning the pain still persisted.
"The player will be sidelined as a precaution for the match against PSG. His evolution will determine his availability for the next training."
Barca began their European campaign with an unconvincing 1-0 triumph over APEOL at Camp Nou earlier this month.
