The expanded list of crimes punishable by death in the small sultanate on the Southeast Asian island of Borneo also includes rape, robbery and insulting the Prophet Mohammed.
The laws, which also call for the amputation of limbs for thieves, make Brunei the first country in East or Southeast Asia to implement the harsh Islamic legal code at the national level. Sharia is practiced to varying degrees in some countries in the Middle East, including Saudi Arabia.
Experts say the draconian death by stoning laws for sex between men and adultery, which can also be punished by caning, are unlikely to be carried out due to the high bar of proof. Brunei has not executed anyone for decades.
The previous law called for a maximum punishment of 10 years in prison for gay sex. Under the new law, women convicted of having sexual relations with other women could face caning or a maximum 10-year prison term.
There has been international condemnation of the legal revisions pushed by Sultan Hassanal Bolkiah, one of the world's richest men, who has wielded power in the tiny tropical nation for nearly five decades.
The UN, Germany, France and the United States have condemned the new laws as incompatible with Brunei's human rights commitments and called for the sultan to reverse implementation.
"Everyone is entitled to live free and equal in dignity and rights," said UN spokesman Stephane Dujarric. "So long as people face criminalization, bias and violence based on their sexual orientation, gender identity or sex characteristics, we must redouble our efforts to end these violations."
Phil Robertson, deputy Asia director at Human Rights Watch, said the code was "barbaric to the core, imposing archaic punishments for acts that shouldn't even be crimes."