Helgenberger,52, made the announcement that the upcoming 12th season will be her last, at a Television Critics Association press conference in Los Angeles.
Helgenberger’s character, Catherine Willows, has been in the show since it began in 2000.
The actress said although the decision to leave was hard, she had been “itching to get back on the stage”.
She said she had considered leaving at the end of the last series, but decided she was “having a hard time letting go” and was “not yet done playing this character”.
“That’s why I decided to extend (my contract) a little bit,” she said.
However the actress hinted she may return to the show in the future, saying: “They’ve always left the door open for me.”
It was announced last month that Ted Danson was joining the cast as the new night-shift supervisor, replacing the outgoing Laurence Fishburne.
The new series begins in the US on 21 September.
I know no one is irreplacable, but Marg’s character Catherine has added compassion and humanity to the ‘science’ of the show and will be sorely missed.
Perhaps Ted could bring in Shelley Long and revive the old partnership. Second thoughts maybe that is not such a hot idea given their differences on Cheers.
It might be more ‘acid’ than ‘Chemistry’.