Ivanek's film credits include Courage Under Fire (1996), Donnie Brasco (1997), Hannibal, Black Hawk Down (both 2001), Unfaithful (2002), The Manchurian Candidate (2004), Live Free or Die Hard (2007), The Bourne Legacy, Argo, Seven Psychopaths (all 2012), and Three Billboards Outside Ebbing, Missouri (2017).

He also appeared as Ed Danvers on Homicide: Life on the Street (1993–1999) and Russell Jackson on the CBS drama Madam Secretary (2014–2019), and has had recurring roles on series such as Oz (1997–2003), 24 (2002), True Blood (2008), Heroes (2009), Big Love (2009–2010), Banshee (2014), and 12 Monkeys (2015–2017).

[3] In 1960, Željko, his younger brother Ivan, and his mother immigrated to Palo Alto, California, where his father was working as a research assistant at the Department of Electrical Engineering at Stanford University.

Having performed in numerous community theater plays in the San Francisco Bay Area, Ivanek graduated from Ellwood P. Cubberley High School in Palo Alto in 1975.

Other roles include Emile Danko in Heroes; Roland in The X-Files; prosecuting attorney Ed Danvers in Homicide: Life on the Street; Ray Fiske in Damages; J.J. in Big Love; the Magister in True Blood; Governor James Devlin in Oz; Serbian terrorist Andre Drazen in 24; and Blake Sterling, the Director of National Intelligence in the NBC drama series The Event.

In the documentary That Guy... Who Was in That Thing, Ivanek states that his contract includes a rider to ensure that the first letter in his name, Ž, has its caron properly rendered in any credits sequence where his name appears.