Her character, Samantha Wheeler, was described in a news release as "a talented new partner at Pearson Specter Litt who challenges the status quo and will either become the firm's greatest ally ... or most powerful enemy."
Season 8 is to begin production April in Toronto.
"Joining 'Suits' was the perfect organic way to not only collaborate with an executive producer I admire deeply, but to also become part of a show and cast that I am an immense fan of," Heigl said in a statement Wednesday.
"I have watched 'Suits' from the very beginning and feel incredibly lucky to be the newest member of the Pearson Specter Litt family."
"On behalf of the entire 'Suits' team, I am extraordinarily excited to welcome Katherine Heigl into our family -- I have always been a big fan of her work and was delighted to discover she was an avid Suits fan herself," added Aaron Korsh, creator and executive producer of "Suits."
"I cannot wait to have her come play with our entire cast and crew. Unfortunately, the same cannot be said for Harvey, Louis, Donna and Alex as the mysterious Samantha Wheeler is a direct threat to their status quo. One thing is for sure -- Samantha's wit, charm, loyalty, strength and vulnerability will all be put to the test as she muscles her way into the firm currently known as Pearson Specter Litt."
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Heigl lives in Utah with her husband Josh Kelley and their three children.
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