Koman was born in Bielsko-Biała, Poland, to actors Halina Koman (née Dobrowolska; born 3 January 1923) and Adam Koman (24 December 1922 – 1 December 2005), and came to Australia in 1982 with his brother Tomek. They landed in Perth before heading over to Melbourne, where he began acting again. Koman attended the National Film School in Łódź, where he studied acting, between 1974-78.
His first professional stage appearance was as a Lysander onstage in Bielsko-Biała, Poland in a production of A Midsummer Night's Dream in 1978.
In Melbourne, Koman met his partner, Australian Actress Catherine McClements, in the late 1980s at the Anthill Theatre. They now have two children together – Clementine Coco (born July 2001) and Quincy (born May 2007). The couple have worked together a number of times, including films Redheads and Floodhouse, as well as an episode of Rush in 2009, and theatre productions Cruel and Tender (2005), Macbeth (2003), The Blind Giant is Dancing (1995) and Angels in America (1994).
Koman is also the lead singer of VulgarGrad, a Melbourne band who play Russian-style music and who formed in 2004.
In 2011, he was nominated for an AACTA award for his guest performance in Spirited. In 2012, he appeared as "The Great Hypno" in the Australian television series Miss Fisher's Murder Mysteries. In 2013, he returned to the stage after an eight-year absence, in Tom Holloway's translation of Durrenmatt's Dance of Death at the Malthouse Theatre in Melbourne.
