The Spanish city was rocked after 13 people were killed and at least 50 injured when a van ploughed into pedestrians on Las Ramblas – a popular tourist district.
Lionel Messi led the tributes for the victims, and he was joined by Barca team-mates Luis Suarez and Gerard Pique, as well as Real Madrid's Cristiano Ronaldo and Sergio Ramos.
And Camp Nou will pause pre-game on Sunday to honour those who lost their lives on the busy street.
"FC Barcelona wants to express their profound sorrow and utter disgust at the terrorist attack that has hit the heart of our city, la Rambla de Barcelona.
"The club wishes to send our support and thoughts to the victims, their families and friends as well as the people of Barcelona and its visitors," the club said in a statement.
"As a mark of respect, the flags will fly at half-mast at the club's facilities and the players from both teams will wear black armbands in all the club's matches this weekend.
"On Sunday, before the 2017-18 La Liga opener against Betis, the Camp Nou will hold a minute's silence in recognition and memory of the victims."