James Edison "Jimmy" Darmody (played by Michael Pitt) is an Atlantic City criminal. Jimmy is the son of one-time Atlantic City boss Commodore Louis Kaestner and showgirl Gillian Darmody. Gillian was just 13 when The Commodore raped her and her relationship with Jimmy was marred by her sexual abuse.

Jimmy was raised by Gillian with support from The Commodore's lieutenant Nucky Thompson. Nucky eventually replaced The Commodore as the boss of the organization controlling Atlantic City. Nucky hoped Jimmy would one day succeed him and sent him to Princeton to obtain a degree.

While at Princeton Jimmy dated Angela Ianotti and she became pregnant with his son. He dropped out of Princeton after sleeping with Gillian. He joined the US Army and served as a machine gunner during World War I. His son Tommy Darmody was born while he was fighting in the war. During his service in France his right leg was injured by shrapnel from a German grenade causing him to walk with a limp.

He then returned to Atlantic City after recovering from his injuries.