Pat Mills's first feature film, the dark comedy Guidance, which he wrote, directed and starred in, had its world premiere at the 2014 Toronto International Film Festival. Picked up by Strand Releasing in the USA and Search Engine Films in Canada, Guidance was hailed as a "Grade A" comedy by the Los Angeles Times and was a New York Times Critics' Pick. His performance as "David" was nominated for an Actra Award for Outstanding Male Performance.

An alumnus of NSI, CFC as well as TIFF's Talent lab and TIFF Studio, Pat was named winner of TIFF's Pitch This for his second feature Don't Talk to Irene. The screenplay won Best Comedy Screenplay at the Austin Screenplay Competition. Released in 2018 starring newcomer Michelle McLeod, Bruce Gray, Scott Thompson and Geena Davis. Don't Talk to Irene had its world premiere at TIFF 2017 and went on to win the Comedy Vanguard Feature Award and Audience Award at the 2017 Austin Film Festival, Audience Choice at the 2018 Kingston Canadian Film Festival, the Galet d'or (Grand Prize) at Festival du film Canadien en Dieppe, as well as two Canadian Comedy Awards: Best Writing in a Feature and Best Feature.

Pat was listed as one of MovieMaker Magazine's 25 Screenwriters to Watch and was University of Toronto's Universal Studios Screenwriter-in-Residence in 2018-19.

He is represented by Great North Artists Management in Canada and Verve Talent and Literary Agency in the USA.