The Pope will allow women to vote for the first time at a crucial global assembly of bishops in October, a decision that has been hailed as a historic first.
The new regulations, revealed on Wednesday, will grant vote rights to five religious sisters at the synod, a papal consultative council.
Women were previously only permitted to attend the assembly as observers.
Men will continue to cast the vast majority of ballots at the key event.
Nonetheless, the reforms are regarded as a big step forward for the Roman Catholic Church, which has been ruled by men for centuries.
The reform has been described as "a significant crack in the stained glass ceiling" by the Women's Ordination Conference, which campaigns for women priests in the United States.
"For years Vatican representatives and bishops resisted, moving the goalpost with every synod as to why women were not allowed to vote," the group wrote on Twitter. "The unspoken reason was always sexism."
"In the near future, we hope that the synod continues to develop into a fully representative body of the people of God."
Pope Francis declared that 70 specially chosen non-clerical members of the religious community would also be granted voting rights, breaking yet another convention and making the synod less exclusively a gathering of the Church hierarchy.
The Pope, a reform advocate, has stated that he wishes half of them will be women, and there has also been a focus on integrating young people.
"It's an important change, it's not a revolution," Cardinal Jean-Claude Hollerich, a key synod organizer, said.
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