Crown Prince Sultan bin Abdulaziz al-Saud was buried in Riyadh on Tuesday.
Prince Sultan died in a New York hospital from colon cancer on Saturday.
His relatives looked on as he was laid to rest.
He served as defence minister and oversaw a spending spree that made the kingdom once of the world’s biggest arms buyers.
Observers expect King Abdullah to name Interior Minister Prince Nayef as the new heir to the throne of the world’s top oil exporter.
Officials from across the Arab and Islamic worlds came to pay their respects.
Iran sent its foreign minister in an apparent bid to ease tensions amid allegations that Iranian agents plotted to kill the Saudi ambassador in Washington.
Sudanese President Omar al-Bashi and Afghan President Hamid Karzai also flew in the service.
From Egypt, military ruler Field Marshal Hussein Tantawi was also in attendance.