The writer of more than fifty episodes for the television serial Sons and Daughters (1984-87), Greg Haddrick also wrote episodes for The Flying Doctors around the same period. He later contributed scripts to such series as All Together Now (1991), Blue Heelers (1994), Mirror Mirror (1995), Home and Away (1988-96) and All Saints (1998).
Since 2000 Haddrick has been a scriptwriter for The Magic Pudding (2000 feature film), My Husband My Killer (2001 telemovie), MDA (2002-03), the telemovies The Society Murders (2006), The Informant (2008) and False Witness (2009). Between 2008 and 2010 he also collaborated with Felicity Packard and Peter Gawler to write episodes for the trio of Underbelly series (based on the 2004 true crime book Leadbelly: Inside Australia's Underworld Wars by John Silvester and Andrew Rule). Haddrick also produced 18 of the episodes.