The accused, who were all Muslims, had pleaded guilty, the head of Kano’s religious police, Aminu Ibrahim Daurawa, told the BBC.
The trial was speedily done in secret after a section of the court was burnt down by angry protesters last month.
It is not known if they will appeal against the sentence.
The alleged offence was committed last month at a religious gathering in honour of Sheikh Ibrahim Niasse, the Senegalese founder of the Tijaniya sect which has a large following across West Africa.
“There has been consensus among Muslims scholars that insulting the prophet carries a death sentence,” Mr Daurawa told the BBC Hausa service.
“We quickly put them on trial to avoid bloodshed because people were very angry and trying to take law into their hands,” he added.
Kano has a predominately Muslim population and Islamic courts operate alongside secular courts.
There were jubilation in some parts of the city as news of the judgement trickled in.
Several states in predominantly Muslims northern Nigeria have introduced Sharia law after the country returned to civilian rule in 1999.
BBC Nigeria analyst Naziru Mikailu says this is the first time a death sentence has been handed down for blasphemy in northern Nigeria.
The sentence has been delivered for other offences such as adultery but none has been carried out.