People were seen laying flowers at a growing pile of floral tributes, while long lines formed at a Sydney blood centre after a call for donations.
At least 38 people were being treated in hospitals after the massacre on Sunday, when the two shooters fired indiscriminately on the beachfront festivities.
Those killed included a 10-year-old girl, a rabbi and a Holocaust survivor.
Australian authorities declared the incident a terrorist attack. One gunman was fatally shot by police and the second arrested.