O'Brien has appeared in numerous miniseries, including The Day of the Roses and Through My Eyes (the story of Lindy Chamberlain).
He has also guest starred on numerous television series, including Halifax f.p.. For his work, O'Brien has won Australian Film Institute and Logie Awards.
In 2009 he played Sydney underworld figure and racing identity George Freeman in the series Underbelly: A Tale of Two Cities.
[2] He also appeared in ITV police drama The Bill in which he played corrupt Detective Inspector Peter Cavanaugh.
[4] In 2022, it was announced O'Brien had reprised his role of Shane Ramsay in Neighbours following the news that the serial would be concluding later that year.