The Catalan club released a statement saying: "FC Barcelona announces that the third match of the Champions League round of 16 will be played on Tuesday, October 21, against Olympiacos at the Estadio Olimpic Lluis Companys."
Hopes had been raised earlier that Barcelona could reopen Camp Nou in time for the La Liga fixture against Girona on 18 October.
However, the club admitted that delays in securing the necessary administrative permits and adapting to new amendments from the Barcelona City Council had pushed back the return.
"Within this framework, FC Barcelona is working on the new amendments that Barcelona City Council shared with the Club last week," the statement added.
It is now expected that Barcelona may continue to play at Montjuic until November, as a partially opened Camp Nou would only hold 27,000 supporters.
In contrast, Montjuic offers a larger capacity and higher revenue opportunities. The plan is for phase 1B of the redevelopment to be completed by next month, which would allow around 45,000 fans to return to the stadium.
The club expressed its gratitude to the supporters for their patience throughout the project, stating: "FC Barcelona thanks its members and fans for their understanding and support during such a complex and exciting process as the return to the new Spotify Camp Nou."
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