The Cairo Criminal Court said Wednesday the six were found guilty of killing three people, including a policeman, among other charges. The case includes a total of 70 defendants.
The verdict can be appealed, and the judge can rule independently of the Grand Mufti.
Egyptian authorities have carried out a far-reaching crackdown on Brotherhood members since a 2013 military coup which removed the country’s first democratically-elected president.
Egypt’s courts have sentenced to death or lengthy jail terms hundreds of people after speedy mass trials, including former president Mohamad Morsi and several leaders of his Brotherhood movement.
Many have appealed and won retrials but 26 executions have been carried out.
The Brotherhood was outlawed and branded a terrorist organisation in December 2013, just months after Morsi was removed from power.