We are often asked: are Catholic nuns allowed to become ordained? Our answer is yes. And no.

We’ll start with the “no.” Current canon law and the church’s catechism directs that “only a baptized man validly receives sacred ordination” to serve as a priest — and only male priests can lead a parish of Catholic Christians, celebrate Mass, and bring new members into the church through Baptism.
However, while they are not permitted to celebrate Mass, nuns may become ordained in compliance with state law, which does not restrict sisters from performing marriage ceremonies as an Officiant.
Ordination through First Nation Ministry complies with all state laws, and is respectful of church law as well. Your title when ordained is “Officiant,” so you are not treading in territory reserved solely for priests within the Catholic church.
…Assuming that there are no obvious impediments to marriage, a lay Catholic who is qualified by the state to preside at civil marriages may do so for non-Catholics who are not bound by Catholic marital law.
— Catholic Answers
In nearly all cases, nuns ordained as Marriage Officiants are not permitted by the Catholic church to perform wedding ceremonies within a parish-owned church building, but they can perform marriages in other facilities, such as public halls, parks, restaurants or private homes.
(Most convents do not permit marriage ceremonies to be performed on site under any circumstances.)
While it is still not common for nuns and sisters to serve as ordained Wedding Officiants — we know of only a dozen or so currently in the United States — there are no legal impediments to serving, although you should discuss the situation with your convent’s superior prior to seeking ordination.
Are you ready to become ordained as a Wedding Officiant?