They say they contain prohibited substances, such as those from pigs, a newspaper said yesterday.
But the injections will be allowed to help alleviate medical conditions such as cerebral palsy, the New Straits Times said.
While the fatwa did not have the force of law, those who ignored it were committing a sin, it said.
Even in medical treatment, the injections must only be provided by a specialist in dire cases, said Shukor Husin, chairman of the National Fatwa Council.
“Since its introduction, there have also been many fake products in the market, and that is another reason why it is haram,” he said, using a term Islam applies to all that is prohibited to the faithful.
The council is the only body officially mandated to issue religious decrees in a nation where just over half the population of 26 million is Muslim.
Botox is a powerful neurotoxin growing in popularity for cosmetic uses, since it paralyses facial muscles, giving foreheads a relaxed, wrinkle-free appearance.