The commemoration Thursday included the symbolic burial of the remains of more than 400 victims of the 1995 genocide, the Birn Justice Report said.
"I ask you not to forget us tomorrow," said Camil Durakovic, president of the commemorative board, addressing the crowd.
He urged them to "work to make Srebrenica a place of peace and tolerance" to send a message that "this will never happen again."
"This is horrible, painful," said Zumra Sehomerovic, whose husband died during the massacre. "I cannot explain to people my pain and sorrow, when I see the horror of this suffering, all these graves."
Noting the massacre occurred in a United Nations-protected area, Bakir Izetbegovic, Bosnia's member of the country's tripartite presidency, said it would always be "a dark stain on the palm of the international community."
The International Criminal Tribunal for the Former Yugoslavia and Bosnian courts has imposed sentences totaling more than 500 years for war crimes committed the Bosnian conflict. Several trials are continuing.
The Serbian parliament expressed respect for the victims, saying in a statement it would "always be committed to preserving the memory of the victims of the brutal armed conflicts," the Serbian Tanjug news agency reported.
The National Assembly said it hoped all the member countries of the former Yugoslavia "will continue the process of reconciliation and facilitating coexistence."