The show is to begin its third season this fall.
Lahti will portray Doris McGarrett, the thought-to-be-deceased mother of Steve McGarrett, played by Alex O'Loughlin.
"The mysterious character of Doris McGarrett is a pivotal one to the mythology of our show," Executive Producer Peter Lenkov said in a statement, "and we are thrilled to have a seasoned and beloved actress such as Christine to portray her. She's a wonderful addition to the 'H5-0' family and the fans will certainly enjoy what we have in store for her. Let's just say that the apple doesn't fall far from the tree."
Lahti earned her first Oscar nomination for "Swing Shift," then took the statue home 10 years later as a first-time director for her short film "Lieberman in Love."
In 1998, Lahti won both the Emmy and her second Golden Globe Award for her portrayal of Dr. Kathryn Austin on TV's "Chicago Hope."