The X-Files actor plays Harris Ryland, the scheming ex-husband of Ann Ewing (Brenda Strong), in TNT's soap revamp.
Pileggi - who appeared in five of the first season's ten episodes - will become a full-time cast member for season two, Deadline reports.
The 60-year-old actor's past credits include stints on Grey's Anatomy, Supernatural, Sons of Anarchy and Stargate: Atlantis.
A second season of the new Dallas was confirmed by TNT in June, with the first run premiering to nearly 3m viewers on Channel 5 in the UK earlier this week.
The series continues on Wednesdays at 9pm on Channel 5 and will return to US screens in January 2013.
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Watch the cast of Dallas speak to Digital Spy below: