He has received five BAFTA nominations, winning once for Most Promising Newcomer for Control—which also earned him an Evening Standard British Film Award for Best Screenplay.

[12] Greenhalgh wrote the 2009 film Nowhere Boy, about a young John Lennon, which was directed by Sam Taylor Wood and starred Aaron Johnson.

[15] In 2010, Greenhalgh wrote and directed the short film, Acid Burn, which starred Agyness Deyn and Matthew Beard.

[16] In 2011, he directed the script for the short film, Supermarket Girl, which starred Matthew Beard and Nichola Burley.

[21] In July 2022, it was announced that the feature film Back to Black, based on the life and career of late singer Amy Winehouse had been scripted by Greenhalgh, with Sam Taylor-Johnson directing the movie.