In a Security Court petition filed on Tuesday, Principal cited irreconcilable differences as the reason for her split from her husband, Dr. Harry Glassman, according to court papers.
Principal and the plastic surgeon were married June 22, 1985, and separated on March 25. They have a prenuptial agreement, according to the petition.
Principal and her first husband Christopher Skinner divorced in 1980.
Her attorney, Judith Forman, declined to comment Thursday.
Telephone messages left for Glassman at his office were not immediately returned.
Principal, 60, rose to prominence as Pamela Barnes Ewing, the stylish, reconciled wife of oilman Bobby Ewing on the hit CBS series. She left "Dallas" in 1987 after nine years with the show.
She also appeared in films "The Life and Times of Judge Roy Bean" and "Earthquake."
The actress has written books on diet and exercise. In addition, she markets her own skin care and makeup lines.