Foy was born in Dublin and graduated from the National Film School.
In 2006, Foy directed an award-winning short film The Faeries of Blackheath Woods based on his own script.
In 2012, Foy wrote and direct his feature film debut an Irish psychological horror Citadel, starring Aneurin Barnard in the lead role. The film got premiered at the South by Southwest festival on March 11, 2012 and won several awards.
Foy directed supernatural horror film Sinister 2 for Blumhouse Productions, starring James Ransone and Shannyn Sossamon. The film was written by Scott Derrickson and C. Robert Cargill, and was released on August 21, 2015 by Focus Features' label Gramercy Pictures. Derrickson secured Foy the directing job of the film after watching his debut film Citadel.
Foy is set to direct an 1960s Ireland-set elevated thriller film The Shee, producing by Blumhouse's Jason Blum, Alan Maher's Roads Entertainment and Foy's Shadow Aspect.