Van der Sloot, 24, is charged with killing Stephany Flores exactly five years after the unsolved disappearance of American teen Natalee Holloway, who was seen leaving a nightclub in Aruba with Van der Sloot. Her body has never been found.
Authorities said Van der Sloot confessed to killing Flores, claiming he became enraged after she discovered his connection to Holloway. His murder trial opened last week but was adjourned to Wednesday after he asked for more time to decide how to plead.
Prosecutors argue that Van der Sloot killed Flores in order to rob her after learning she had won money at the casino where the two met.
Van der Sloot entered the plea in hopes of a reduced sentence. The panel of three judges has 48 hours to render a sentence.
The Associated Press contributed to this report.