The Brooklyn star plays a domestic abuse victim in the promo for Cherry Wine.
Announcing the news on his website, the Take Me to Church singer writes, "I tried to get across the difficulty of coming to terms with and facing up to domestic violence and the dynamic of an abuse relationship.
"I'm honoured to be joined by Saoirse Ronan, video director Dearbhla Walsh and Moe Dunford in spreading awareness on this issue."
Dunford plays Ronan's lover in the video, which cuts between shots of the couple laughing and joking together to scenes featuring the actress removing her makeup in a mirror to reveal a black eye.
The video was shot as part of the #FaceUpToDomesticViolence campaign, and proceeds from downloads of Hozier's new song will benefit various domestic violence charities.