The operators of the Westfield mall, about 3 kilometers (2 miles) from the city's iconic Bondi Beach, allowed residents enter to pay their respects to the victims, with stores remaining closed and a white floral tribute laid out on the second floor.
Many wept as they walked though the halls, with advertisements on digital screens replaced by black ribbons.
Normal trading will resume on Friday, while a candlelight vigil at the beach on Sunday will mourn the victims, authorities said.
"It wasn't very nice walking through there, it obviously did bring back certain flashbacks," said Vinny Jovanovski, 33, who owns the Glo Bar cafe on the fifth floor of the mall and witnessed the attacks. "But I mean, we have a lot of love and support from the community. Everybody is being very kind to each other."
Sydney, one of the world's safest cities, suffered its second high-profile stabbing in three days on Monday after police said a teenager stabbed a bishop in the city's west.
Saturday's attacker, 40-year-old Joel Cauchi, suffered from mental health issues, police and his family said.
Wearing shorts and an Australian national rugby league jersey, he ran through the mall with a knife, fatally stabbing six people and injuring at least 12 before he was killed by Inspector Amy Scott.
Some shoppers and staff at the mall in Sydney's east tried to stop him, including Damien Guerot of France, who has become known as "Bollard Man" after holding back Cauchi with a post from a queue barrier.
Martine Wachtenhein, 66, who was among those visiting the mall on Thursday, choked back tears as she recounted how Cauchi came within three or four meters of her before Guerot forced him back.
"I could have been one of the people stabbed," she said, choking back tears. "If I could send a message to that beautiful man that would be the best thing... I want to thank him. I don't think he realises the impact it had on me; thanks to him I managed to escape."