The amendment will now go before Switzerland's Council of States before a referendum can be held.
ADVERTISEMENTSwiss lawmakers have voted to expand the country's definition of rape to state that explicit consent is required for all sexual acts.
Under current legislation, rape is only defined as "coerced" penetration if a woman had shown some degree of resistance.
The "only yes means yes" amendment narrowly passed on Monday with 99 votes in favour, 88 against, and three abstentions.
Amnesty International has hailed the vote as "a huge success after years of political activism by activists defending women's rights and victims of sexual violence".
Several European countries -- including Denmark and Spain -- have recently changed the law to define rape as sexual assault without explicit consent.
Some conservative Swiss politicians have argued for a "no means no" approach to the country's rape laws, where rape cases are only brought if a person explicitly objects.
But socialist lawmakers have rejected arguments that the "only yes means yes" law would be difficult to enforce.
"It goes without saying that you don't take money from your neighbour's wallet without asking him," said Social Democratic Party MP Tamara Funiciello, according to the ATS agency.
"It goes without saying that you don't enter someone's house without ringing the bell. Why my wallet and my house would be better protected than my body?”
"The body of the other is never an open bar," added Green MP Raphaël Mahaim. "Before having a moment of sexual sharing, you must ensure the consent of your partner".
The amendment will now go before Switzerland's Council of States before a referendum can be held.