While the royal place has the "maximum respect" for the decision, it "wants to express its surprise for the change in position" by the investigating judge who in March 2012 declined to name the princess as a suspect in the case, a spokesman for the royal palace told AFP.
The 47-year-old Infanta must testify as a suspect on April 27 at the court in Palma on the Mediterranean island of Mallorca, said a written ruling by the judge, José Castro.
It is the first time a member of the Spanish royal family has been called to appear in a court of law on suspicion of wrongdoing.
The case, which was opened at the end of 2011, is centred on allegations of embezzlement and influence peddling against her husband, former Olympic handball player Inaki Urdangarin, and his former business partner Diego Torres.
The pair are suspected of syphoning off money paid by regional governments to stage sports and tourism events to the non-profit Noos Institute, which Urdangarin chaired from 2004 to 2006.
Anti-corruption prosecutors plan to appeal the judge's decision to summon the princess as a suspect due to "the complete lack of evidence of participation in any criminal act", a judicial source said, a decision which was welcomed by the royal palace.
"The royal palace also wants to express its complete agreement with the decision announced by anti-corruption prosecutors to appeal this ruling," the spokesman for the royal palace said.