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.
The nine, eight man and a woman, were reported to have said that "Niasse was bigger than Prophet Muhammad", triggering unrest.
The venue was burnt to the ground by an angry mob and the nine were arrested,
"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.
BBC Kano reporter Yusuf Yakasai said people celebrated in some parts of the city when news of the judgement emerged.
The Sufi sect of Tijaniya was founded in Algeria in 1784 by Ahmad ibn Muhammad al-Tijani.
It spread all over the world, with large following in north and west Africa. It also has followers in South Africa, Indonesia and other parts of the world.
There are other Sufi sects in Islam but Tijaniya is the largest.
They have three main daily practices: Asking the forgiveness of God; sending prayers to the Prophet Muhammad and affirming the Oneness of Allah.
Senegalese-born Sheikh Ibrahim Niasse was credited with reviving the sect in the 20th Century. People travel from across the continent to visit his shrine.
They have several factions including the Haqiqa (Realist) group, whose leaders were convicted accused of blasphemy in Kano.
Several states in predominantly Muslims northern Nigeria have introduced Sharia law after the country returned to civilian rule in 1999.
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.