Although the glamorous royal is not staying the night in Vienna, she has rented a suite at the city's iconic Hotel Sacher, The Local Austria reports.
She will have lunch with President Heinz Fischer, and will reportedly then visit a social project for young people, seeking inspiration for a similar project in Spain.
The Velazquez exhibition opens at 6.30pm. It is the first major exhibition devoted to the Spanish court painter in the German-speaking world.
"We will make sure that the Queen of Spain can pass through the museum unhindered. Everyone will want to see her and photograph her and we will have set up several areas where she can be photographed,” said Kunsthistorisches Museum director Sabine Haag.
Queen Letizia will deliver a speech in English to 180 guests and 24 ambassadors in the museum’s domed hall.
Letizia is a former newsreader who worked for Bloomberg TV and CNN.