Zappone was a prominent campaigner for the Yes campaign in Ireland's Marriage Equality referendum, featuring on an RTÉ Primetime debate, helping YesEquality as a voluntary adviser, taking part in debates, and campaigning for a Yes vote. On 22 May 2015, she spoke about how she believed Irish people would "vote Yes for equality; for a Republic of equals, a Republic of love". On 23 May 2015, Zappone asked her wife Ann Louise Gilligan live on air to remarry her in Ireland now that it had voted yes to marriage equality. She described how she was "feeling emotional from the top all the way down to my toes".