The Terminator 2 actor will join the HBO vampire drama as Alcide Herveaux's father Jackson, according to The Hollywood Reporter.
Patrick's character will be introduced in a flashback episode showing the cast in the 1980s entitled 'Everyone Wants to Rule the World'.
The flashback, which will show Alcide (Joe Manganiello) and Debbie Pelt (Brit Morgan) as teenagers, will also contrast Jackson's inspiring and heroic attitude then with a more downtrodden personality in the present day.
Patrick was recently granted series regular status on ABC's action thriller Last Resort. His other previous TV credits include The X-Files, The Sopranos and The Unit.
He is tipped to make his True Blood debut on August 5.
True Blood airs on Sundays at 9/8c on HBO in the US. It will air on FX in the UK later this year.
Watch a True Blood season five trailer below:
Gallery - 'True Blood' season five character posters: