Theresa May also reiterated her belief that it was ultimately up to the church to decide its own position on the matter, during an interview marking half a century since the decriminalisation of homosexuality in England and Wales.
Speaking with LBC, she said: "The Church of England has itself come a distance in terms of looking at these issues. And obviously they will want to reflect as attitudes more generally change, as society changes."
The leader also suggested that her late father, Anglican vicar Rev Hubert Brasier, might have approved of Church of England clergy blessing gay marriages. Mrs May has previously spoken openly about her own Christian faith.
She went on to say: "He very much valued the importance of relationships, of people affirming those relationships and of seeing stability in relationships and people able to be together with people that they love."
Mrs May held a reception at Downing Street on Wednesday evening to mark 50 years since the Sexual Offences Act 1967.
Her radio interview comments came on the day after House of Commons speaker John Bercow addressed a gay newspaper event in Parliament, where he said marriage equality will only exist with same-sex couples can marry in churches.