The women were on a Christmas camping trip and were studying to become tour guides.
A fourth man said he left the group before the murders was given a life sentence.
Prosecutors have already called for the death penalty for the three main suspects behind the killings in the High Atlas mountains last December.
Two of them - Abdessamad Ejjoud and Youness Ouziyad - had told the court they had decapitated the women, while the third - Rachid Afatti - said he filmed the killing and posted the footage online.
He and two others admitted to killing 24-year-old Danish student Louisa Vesterager Jespersen and 28-year-old Norwegian Maren Ueland in murders that shocked the North African country.
The three main defendants sentenced to death on Thursday were ringleader Abdessamad Ejjoud, a 25-year-old street vendor and underground imam, Younes Ouaziyad, a 27-year-old carpenter, and 33-year-old Rachid Afatti.
The Moroccan court also handed 19 accomplices jail terms ranging from five to 30 years.
The bodies of the two women - roommate at Norway's Bo University - were found on December 17 in an isolated area near Mount Toubkal, Morocco's highest peak, and a popular hiking destination.
Helle Petersen, her mother, in a letter read out in court last week, said: 'The most just thing would be to give these beasts the death penalty they deserve'.
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A Swiss-Spanish convert to Islam, Kevin Zoller, who had pleaded innocent, received a 20-year sentence.
If the executions plod forward, they might maybe be the first in Morocco since 1993.
All but three of those on trial had said they were supporters of the Islamic State group, according to the prosecution, although IS itself has never claimed responsibility for the murders.
The prosecution described the three killers "bloodthirsty monsters", the prosecution said, citing an autopsy report that found 23 injuries on Jespersen's body and seven on that of Ueland.
Their defence team talked about there had been "mitigating conditions on legend of their precarious social prerequisites and psychological disequilibrium", AFP reported.
The Scandinavian women were killed in their tents near the Moroccan village of Imlil, a popular hiking destination in December previous year.
"We're going to appeal", said his lawyer, regretting that the judges hadn't taken into account "proof of his innocence".
Moroccan authorities had been criticised by Ms Vesterager Jespersen's lawyer for failing to monitor the suspects' actions, which can also have averted the girls being killed.
Security forces guard a courtroom before the start of a final trial session for the suspects charged in connection with killing Ueland and Jespersen.