The decision, made by a unanimous court of one professional judge and two lay judges, was announced at 1pm on Wednesday by Copenhagen District Court. His lawyer immediately said he would appeal the verdict.
Madsen, 47, had admitted dismembering 30-year-old Wall's body and throwing her remains overboard in waters off Copenhagen last August, but claimed her death was accidental.
But he changed his version of events several times, and the court found he had failed to give any credible explanations.
He initially claimed he had dropped Wall off on dry land in Copenhagen on the night of August 10th, 2017, after she boarded his submarine Nautilus to interview the eccentric self-taught engineer.
But he soon changed his story, claiming that a heavy hatch door had fallen on her head and killed her.
When the autopsy later revealed there was no blunt trauma to Wall's skull, he said she died after a sudden drop in pressure caused toxic fumes to fill the vessel while he was up on deck.
Prosecutor Jakob Buch-Jepsen on the other hand told the court during the 11-day trial that Madsen killed the journalist as part of a macabre sexual fantasy and "tried to create the perfect crime".
The court also found Madsen guilty of sexual assault and desecrating a corpse.
Despite the testimony of many experts, the lack of tangible evidence in the case and the decomposed state of Wall's remains made it impossible to determine her exact cause of death.
An autopsy report said she probably died as a result of suffocation or having her throat slit.
But the court found the incriminating circumstances were enough to find Madsen guilty, including the gruesome videos he watched, and the fact that he brought a saw, plastic strips and a sharpened screwdriver on board.
Psychiatric experts who evaluated Madsen – who described himself to friends as "a psychopath, but a loving one" – found him to be "a pathological liar" who poses "a danger to others" and who was likely to be a repeat offender.
Madsen is the 15th person in 10 years to receive a life sentence in Denmark.