The letter, stating it is from the US embassy in Riyadh, is among about 70,000 documents dubbed "The Saudi Cables" the whistleblower website published.
They are among more than half a million cables and other documents from the Saudi foreign ministry and other institutions in the kingdom which WikiLeaks says it will release over the coming weeks.
The letter is signed by Glen Keiser, the US consul general in Riyadh and addressed to Abdullah bin Laden on September 9, 2011, about four months after a US raid killed his father in Pakistan after a decade-long manhunt.
"I have received your request for a death certificate for your father, Usama bin Laden," Keiser wrote.
Legal experts in the State Department advised that no such document was issued, he said. "This is consistent with regular practice for individuals killed in the course of military operations."
Instead, Keiser provided Abdullah bin Laden with US court records in which officials confirmed his father's death and, as a result, dropped a criminal case against him.
"I hope that these US government documents are of assistance to you and your family," Keiser said. The bin Ladens are a prominent Saudi business family. The kingdom stripped Osama bin Laden of citizenship in 1994.