He has worked extensively in television, directing numerous episodes of CSI: NY, Treme, True Blood and Shameless, among others.
Hemingway began working in the industry on Tom Fontana's HBO prison drama Oz as an assistant director.
He was the first assistant director on the film Freedomland in 2006 which was written by The Wire writer Richard Price and featured several cast members from that show alongside Samuel L. Jackson.
He first worked with director/producer Joe Chappelle on the 2000 film Takedown and has since collaborated with him on The Wire and CSI: NY.
HBO is also developing Bros, a comedy set to be directed by Hemingway and written by Ben Cory Jones, that centers on three African-American brothers — two straight and one gay — who are each dealing with love and dating.