The prince was received at the airport by Argentina's foreign minister Jorge Faurie, according to Argentine press.
The Saudi foreign ministry tweeted video footage of the crown prince getting off a plane in Buenos Aires.
"Crown Prince Mohammed bin Salman arrives to Argentina to head the delegation participating in the G20 summit," said a royal court statement carried by the official Saudi Press Agency.
Officials said the prince could meet Turkish President Recep Tayyip Erdogan on the sidelines of the summit.
Protests as Saudi crown prince visits Tunisia
That would be the first meeting of the two since Khashoggi's brutal killing at the Saudi Arabian consulate in Istanbul on October 2.
"There could be" a meeting, Turkish presidential spokesperson Ibrahim Kalin said.
Argentina was meanwhile due to decide whether to launch an investigation into him over the journalist's murder and possible war crimes in Yemen.
On Monday Kenneth Roth, the executive director of Human Rights Watch, an international rights group, asked Argentina to open the probe.
Hundreds protest in Tunisia at Saudi Crown Prince visit
"A decision by Argentine officials to move toward investigation would be a strong signal that even powerful officials like Mohammed bin Salman are not beyond the reach of the law," Roth said in a statement.
"And Mohammed bin Salman should know that he may face a criminal probe if he ventures to Argentina."
Saudi Arabia has faced sharp international criticism over the murder of Washington Post contributor Khashoggi.
The journalist was killed and dismembered in what Saudi Arabia said was a "rogue" operation — though CIA analysis leaked to the US media appeared to implicate Prince Mohammed.
Saudi Arabia's Crown Prince Mohammed bin Salman will attend the G20 summit
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