The law comes after strong protests after a woman was gang-raped in front of her children when her car broke down on a motorway in September.
Special courts will be set up across the country to speed up trials involving rape cases, Pakistani President Arif Alvi wrote on Twitter.
Must be approved
However, the law will need to be approved by Parliament within 120 days in order to remain in force in the future.
In the past, rape cases could have lasted for several years, as a result of poorly conducted investigations and deficient laws.
Now both the trial and the verdict will be ready within four months.
Negligence is punished
According to the Pakistani newspaper The Dawn, the new law will also mean that officials who are negligent in connection with rape investigations risk up to three years in prison.
Less than three percent of reports of sexual assault and rape lead to convictions in Pakistan, CNN reports.