His body is lying in the parliamentary building in the capital, Kinshasa, and will be taken later to his family home for the public to view.
Papa Wemba will be buried on Wednesday.
Known as the king of Congolese rumba, the 66-year-old died after collapsing on stage in Ivory Coast on 24 April.
President Joseph Kabila delivered a tribute to the singer at the memorial held at the parliamentary building, and awarded him one the DR Congo's highest honours for the "loyal and eminent services given to the nation".
An enormous red hat, modelled on the one Papa Wemba was wearing at the time of his death, stood above his coffin.
A life-sized effigy of the singer stood next to it.
Fans from all over DR Congo are attending the memorial, the BBC's Maud Jullien reports from Kinshasa.
These include mourners from the Society of Elegant People, known as the Sapeurs, who saw Papa Wemba as a god of fashion.
Papa Wemba was born Shungu Wembadio Pene Kikumba in June 1949 in Lubefu, in what was then the Belgian Congo.
He was considered one of Africa's most influential musicians and pioneered modern Congolese soukous music, which spread through the continent.
In a career which spanned over four decades, he collaborated with stars like Peter Gabriel and Stevie Wonder.
What made Papa Wemba so influential?
Obituary: Papa Wemba
BBC Papa Wemba playlist
"Papa Wemba brought Congolese music to the world. He showed another part of Congolese music. He's an icon.
Lokua Kanza, Congolese Singer
"Papa Wemba was for me a father.  We lost the biggest artist in DRC. Politicians [from all sides] are [even] prepared to meet because of his death.
Lexxus Legal, Congolese hip hop artist
Thousands of mourners are attending the first day of official commemorations in the Democratic Republic of Congo to mark the sudden death of music star Papa Wemba.