Van der Sloot admitted killing Stephany Flores, 21, in 2010 in Lima, El Comercio reported. He is to be sentenced on Friday and could get up to 30 years but his decision to plead guilty may result in a reduced sentence, court observers said.
In his admission, van der Sloot apologized for the killing and said he welcomed a quick conclusion to the legal proceedings.
Van der Sloot, now 24, was living in Aruba when Holloway vanished in May 2005 while she was on the island with high school classmates for a trip to celebrate graduation. He quickly became a suspect and was twice arrested but investigators, with no body or proof of Holloway's death, were unable to fix the crime on him.
Flores's body was discovered in Van der Sloot's Lima hotel room on May 31, 2010. Van der Sloot, who took her money and bank cards, was arrested three days later in Chile.
Van der Sloot also faces charges in the United States of trying to extort money from Holloway's family.
Flores, a university student and daughter of a prominent businessman, was killed exactly five years after Holloway disappeared.