The star has been portraying Dr. Addison Montgomery in the Grey's Anatomy spin-off since its premiere in 2007, but she is preparing to hang up her stethoscope for good once filming wraps on the latest run of the U.S. TV show.
She tells new U.S. talk show host Bethenny Frankel, "This is my last season for Private Practice. It's been an incredible journey, an amazing ride. I'm hugely, hugely grateful.
"It's been a long time being Addison and I feel incredibly grateful to (creator) Shonda Rhimes and all the fans that have been there from day one to now, but I'm really excited about the last season.
"It's bittersweet. It's a huge chapter of my life, it's been eight years."
Walsh first starred as Dr. Montgomery in episodes of Grey's Anatomy in 2005.
It is not known whether network bosses at ABC, which airs the show, will continue Private Practice without Walsh.