Urdangarin has been charged with breach of legal duty, embezzling public funds, fraud, influence-peddling and money-laundering. The princess is accused of two tax crimes.
Spain's new king, Felipe VI, will be sworn in later on Thursday in a low-key ceremony which monarchists hope will usher in a new era of popularity.
Spain's lower house of Parliament on Wednesday voted overwhelmingly in favour of urgent government legislation allowing King Juan Carlos to abdicate this month and hand over his duties to Crown Prince Felipe.
Spain's King Juan Carlos, who led Spain's transition from dictatorship to democracy, will abdicate so his son Felipe can become the country's next monarch, Spanish Prime Minister Mariano Rajoy told the country Monday in an announcement broadcast nationwide.
Juan Carlos kept his son and heir Prince Felipe, then aged 13, at his side throughout the crisis. "I wanted him to see what one has to do when one is king," he said later.
Spanish Prime Minister Mariano Rajoy says King Juan Carlos plans to abdicate and pave the way for his son, Crown Prince Felipe, to become the country's next king.