John Howard, who has submitted a written statement to the inquiry, said in a statement on Wednesday he had agreed to a request by the inquiry to appear on Thursday.
He will be the first prime minister to face an official inquiry since 1983.
The inquiry, headed by Terence Cole, a former supreme court judge, has no political brief and can only recommend prosecution of companies and individuals, including the wheat exporter AWB Ltd, if it finds that Australian laws were broken.
A 2005 UN report alleged that the AWB was one of more than 2,000 firms that had paid kickbacks worth $1.8 billion to Saddam's government through the UN-managed "oil-for-food" account between 1997 and 2003.
If that is proven, AWB would have broken UN sanctions against Iraq.
AWB, a monopoly, was government owned until 1999.
Peter McBride, an AWB spokesman, said James Judd, the QC for the board of the wheat exporter, had no intention to cross-examine Howard on the witness stand.
But Howard will be cross-examined by lawyer Terry Forrest, who is acting separately for two AWB executives.