The decision was made by a Stockholm district court on Tuesday.
Lindh died on 11 September, a day after 25-year-old Mijailo Mijailovic attacked her while she was shopping, repeatedly stabbing her in her stomach, chest and arms.
In its decision, the court said Mijailovic was aware of what he was doing when he stabbed Lindh repeatedly, noting that the severity and violence of the attack was severe.
"It was very much expected, it couldn't have gone any other way," said Christopher Diesen, a law professor at Stockholm University. "There were no extenuating circumstances."
Born in Sweden of Serb parents, Mijailovic has a criminal record and was sentenced in 1997 for attacking his father with a kitchen knife.
Swedish media reports speculated that Mijailovic, believed to be mentally unstable, was obsessed by several famous people, and hated Lindh for backing the NATO air strikes against Belgrade during the war in Kosovo in 1999.
Lindh, 46, was widely tipped as a future prime minister. Her death plunged the country into a state of shock and raised the spectre of the unsolved death of Prime Minister Olof Palme in 1986.