The no-show by Francisco Camps was the latest twist in a judicial probe that has raised questions about the future of Spain's monarchy.
Camps, an old ally of Prime Minister Mariano Rajoy, had been called to hand in written witness testimony to a judge on the island of Mallorca, but the court said on Sunday that it could not get hold of Camps.
The court is investigating allegations that King Juan Carlos's son-in-law, Inaki Urdangarin, embezzled public money from the Valencia government via the Noos Institute, a charitable foundation that Urdangarin chaired.
The testimony "will not take place today since the court has not been able to contact the former president of the Valencia region," the tribunal said in a brief statement on Sunday.
"The testimony will be pending until further notice."
Camps, a senior figure in Rajoy's Popular Party, himself was acquitted in January 2012 of accepting bribes in the form of designer suits between 2005 and 2008 while president of the region.
Urdangarin chaired the Noos Institute from 2004 to 2006, while Camps was regional president.
The far-reaching corruption probe has plunged the royal family into its worst popularity crisis since Juan Carlos, 75, took the throne in 1975.
The judge leading the probe, Jose Castro, is also investigating the tax affairs of Urdangarin's wife, the king's youngest daughter Cristina, 48.