The legislation, passed unanimously by the National Assembly, mandates life imprisonment even if the victim's relatives forgive the murderer.
The assembly also passed a bill increasing the punishments for some rape offences, mandating DNA testing and making the rape of a minor or the disabled punishable by life imprisonment or death.
Women have long fought for their rights in Pakistan, and so-called "honour" killings claim the lives of hundreds each year.
Rape conviction rates are close to zero percent, largely due to the law's reliance on circumstantial evidence and a lack of forensic testing.
Rights groups and politicians have for years called for tougher laws to tackle perpetrators of violence against women in the country.
The gruesome murder of Facebook star Qandeel Baloch in July catapulted the issue into the international spotlight.
"This is a step in the right direction," women's activist and columnist Aisha Sarwari told AFP.
"We should take our little wins where we get them and proceed forward and not retreat." Excellent, if you ask me.