The appeals court in Brussels upheld the decision on Monday, after a separate court had approved Van Den Bleeken's right to seek assisted suicide in mid-September.
"He can leave the jail for 24 hours in order to seek euthanasia," a court press spokesman said.
The exact date of Van Den Bleeken's euthanasia is not known.
Seeking an end to 'psychological pain'
Van Den Bleeken was found guilty of murder and rape on multiple instances, and has spent nearly 30 years behind bars. He considers himself a danger to the public. The 50-year-old says he suffers from "psychological pain" that cannot be treated and is unable to control his sexual urges.
"I am a human being, and regardless of what I've done, I remain a human being. So, yes, give me euthanasia," Van Den Bleeken told VRT Flemish Belgian television.
His lawyer, Jos Vander Velpen, defended the court's ruling, saying his "client suffers endlessly."
A sister of one of Van Den Bleeken's victims expressed dismay at the decision. "He should die in his cell," she told the daily Het Laatse Nieuws newspaper earlier this month.
Increase in assisted suicide
After Van Den Bleeken became the first Belgian to be granted the right to euthanasia earlier this month, 15 further long-time inmates in the country asked to seek assisted suicide.
Belgium has allowed assisted suicide since 2002 for the terminally-ill. Across the country last year, 1,807 people opted for assisted suicide, 27 percent more than in 2012.
In February, Belgium became the first country in the world toallow assisted suicide without an age limit. Thus, terminally ill children can choose to take their own lives in certain circumstances.
Among European countries, assisted suicide is also legal in the Netherlands and Luxembourg.
dr/bw (KNA, dpa, AP, Reuters, AFP)