Families of around 8,000 Muslims victims of the massacre were heading to the vast cemetery in Serbia where more than 4,000 white grave stones dot the grounds and 613 more had been newly dug to receive the remains of more victims during the commemoration service.
Ahmed Sehic, 26, has come to bury his father who was killed with two of Ahmed's uncles while trying to flee through the woods to Muslim-held territory.
"I hope it will be easier for me now, I will know where he is, where I can come to visit his grave," he told AFP.
This year's anniversary of the July 11, 1995, massacre in Srebrenica, the worst mass killing in Europe since the end of the World War II, comes only weeks after the arrest of then Bosnian Serb army chief Mladic in Serbia.
Both Mladic and his political chief Radovan Karadzic, who was arrested in 2008, are charged by a UN war crimes tribunal with genocide, crimes against humanity and war crimes.
The Srebrenica massacre, the only episode in the bloody Balkans wars to have been ruled a genocide by international courts, is a key part of their indictments.
Mladic famously visited Srebrenica right after the UN-protected enclave fell and promised refugees gathered in front of the UN barracks, "Do not be afraid, no one will harm you".
His troops had already started separating the men from the women, children and elderly and in the coming days would summarily execute nearly 8,000 men. They were buried in mass graves which were later dug up and the remains scattered over different smaller secondary graves to cover up the scale of the slaughter.
Ahmed recalled that as a boy of 10 years old with his mother among the refugees in Potocari he saw Mladic.
"When I saw Mladic (following his arrest) after all these years I remembered the moment he was only a metre (yard) away from me in Potocari and I cannot comprehend how he is not aware of what he has done and why he does not repent," he said.
Mladic has dismissed the charges against him as "obnoxious" and told the court he was "only defending (his) country"
"I was delighted to hear he was arrested but unfortunately much time has passed... I am afraid he could die before his trial is concluded," Ahmed said.
The ceremony in Srebrenica will be attended by the Bosnian and Croat members of Bosnia's three man presidency, Bakir Izetbegovic and Zeljko Komsic, while hardline Bosnian Serb President Milorad Dodik will send only some representatives.
Croatian President Ivo Josipovic will atend but no high ranking officials from the Serbian government are expected to take part.
"Srebrenica is the deepest wound for Muslims in Bosnia. It is a black spot on the conscience of the international community and on the conscience of those who committed the crime," Bosnia's Muslim member of the presidency Izetbegovic said Saturday.