As a child, Sikora appeared in a McDonald's commercial with Michael Jordan. He made his Broadway debut in 2006 after he was cast as one of the leads on The Caine Mutiny Court-Martial. He is also an ensemble member of Chicago's Shattered Globe Theatre Company. Sikora made his acting debut in an episode of The New Adam-12 after playing extras on a few TV shows. He was cast as Johnny in Rudy. After making small appearances in TV shows and films such as Early Edition, Turks, The Watcher, and Ghost World, he was cast in two episodes of Third Watch. In 2003, Sikora was cast as Roger in the direct-to-video biographical-drama film Gacy. After making a few appearances on low-budget movies, he was cast in the Golden Globe-nominated Normal, which he feels was his "break-through" moment when the star of the movie, Tom Wilkinson, told him that "all you have to do is think the line and the camera will read it". He also took part in plays and was part of the Geffen Theatre's production of Fat Pig and the Los Angeles Theatre's production of Killer Joe. He made many TV appearances between 2005–2012, appearing in major network shows including ER, Grey's Anatomy, Criminal Minds, Without a Trace, ', Prison Break, Lost, and Dollhouse. He was later cast in the 2007 horror film Night Skies. He appeared in the last episode of nypd blue in 2005. He was later cast in two episodes of ' in 2010.That same year He also portrayed Hans Schroeder in HBO’s series Boardwalk Empire As well ashe was cast as an Orderly at the Mental Hospital in Shutter Island. In 2011, he was cast in the television pilot for Body of Proof, as well as being signed in a full role in Adult Swim's comedy horrorTV seriesThe Heart, She Holler, playing Sheriff. In early 2012, he signed on to appear in Safe as the son of the head of the Russian mafia. He returned to theater in September 2012 with The Freedom of the City. In October 2013, he was cast in Starz! original drama seriesPower. In 2012, he appeared in Jack Reacher, in which he played a sniper wrongfully accused of gunning down random people in Pittsburgh, and who requests Jack Reacher's assistance to prove his innocence. Recently, Sikora portrayed Frank Cosgrove Jr. on the third season of the Netflixcrime dramaOzark which was released on March 27, 2020.
