Marshall Napier was born in New Zealand als Marshall James Napier on 22 October 1951. Before becoming an actor, Napier worked variously as an art student, factory worker and truck driver. He has two children daughter Jessica – an actress – and son James Reuben. He is the uncle of James Napier Robertson.

Before moving to Australia with his family, Marshall Napier worked as an actor in New Zealand. He worked in Dangerous Orphans, Starlight Hotel or "The Neville Purvis Family Show" . The last one was his first work for TV 1979. To pursue Marshall’s career in acting the family moved to Australia in 1988. In 1988 Marshall acted as Bill Kennon in the TV series "Always Afternoon". The series told the story of German prisoners of war, as well as Aussies of German heritage, kept in camps in the year 1915. The German actors Jochen Horst and Ben Becker were two of Marshall’s colleagues.

From 1991 to 1992 Marshall acted as Sgt. Fred 'Frog' Catteau together with Sonia Todd and his daughter Jessica in her first TV role in the series „Police Rescue“. Marshall Napier acted in series like "Snowy River: The McGregor Saga", "Blue Murder" or "Blue Heelers" In 1999 he was back at “Water Rats” to play his character Joe Da Silva again like he did in the years 1996 and 1997. He acted in "The Lost World", "All Saints", "Farscape", "Head Start" or Get Rich Quick.

In 2001 he started to play the character Harry Ryan in the series “McLeod’s Daughters” and he ended in 2006 to play in that series. In “McLeod’s Daughters” one of his colleagues was his daughter Jessica.

2007 Marshall Napier acted as Sgt. Strunk in The Water Horse and 2007/2008 you could see him as Wilton Sparkes in the series City Homicide".

In 2009 Marshall Napier acted a one episode character at the series Chandom Pictures.

He acted site by site with his nephew James Napier and his McLeod’s Daughters colleague Michelle Langstone in I am not Harry Jenson.

The period of post-production if The Clinic, where Marshall Napier acted as Officer Underwood, ended.

In 2010 Marshall Napier could be seen at the movie Griff the Invisible as Benson and at I Love You Too in a minor role.

2010 acted Marshall Napier at the Belvoir Street Theatre in the play The Power of Yes as Howard Davies. And he played at the theatre play In the Next Room.

He filmed for the movie Griff the Invisible. In 2011 he could be seen as Chief Commissioner at the telemovie Underbelly Files: Tell them Lucifer was here.

In 2011 he acted at the telemovie Panic at Rock Island.                                       

In 2012 he could be seen at Jake Irish: Bad Debts and Rake. And again he acted on stage. He played at the theatre play The Gift.

2013 he filled in shortly as Big Daddy at the play Cat on a Hot Tin Roof.

2002 Marshall and his daughters Jessica gave their win at “"Who Wants to Be a Millionaire" to the South Australian Animal Rights Group. Both father and daughter supported standing up for animals.

In his 40´s he began to writing theatre plays.