The couple will receive therapy in prison
Daniel and Manuela Ruda never denied killing their victim, but argued it was not murder because they were acting on the Devil's orders.
They received sentences of 15 and 13 years respectively in a secure psychiatric ward.
The decomposing body of the dead man, Frank Haagen, was found in the couple's flat in July with a scalpel protruding from his stomach and the sign of the Devil carved into his chest.
The couple were arrested a week later.
Narcissism
The presiding judge, Arnjo Kerstingtombroke, stipulated that the couple should receive therapy in jail, to ensure that they never repeated their crime.
The defence had called for acquittal on the grounds that the couple were mentally unfit, but the sentences were one year longer, in each case, than the prosecution had requested.
The couple have shown no remorse for their crime and shocked the court with their extrovert behaviour, striking defiant poses for photographers.
Experts told the court in Bochum, in Germany's western Ruhr region, that they were suffering from "severe narcissistic personality disturbances".
Chainsaw
Accounts of the gruesome killing, in a room full of human skulls, cemetery lights, and a coffin in which Manuela slept, have been given detailed coverage in the German media.
Manuela Ruda, aged 23, told the court that Satan had called her when she was 14.
She said she shunned strong light and had become involved in vampirism at "bite parties" in London.
She and Daniel, aged 26, said they attempted suicide during several days on the run after killing their victim, who worked with Daniel selling car parts.
Daniel also bought a chainsaw, saying he did not want to be empty-handed when the Devil called again.