A second season of the USA show - starring Gabriel Macht and Patrick J Adams - will begin shooting shortly in Canada.
Harris will appear in the third episode as a Harvard Law representative who causes problems for Louis (Rick Hoffman), according to The Hollywood Reporter.
The actress, who appeared in 2009 film The Hangover, has previously played guest roles on Cougar Town and Modern Family.
She is also attached to an in-development CBS comedy pilot starring Bridesmaids actor Ben Falcone.
Margo Martindale (Justified, A Gifted Man) will also appear in the new season of Suits as a nurse, while Eric Close (Without a Trace) will also reprise his role as Travis Tanner.
The series is expected to return to USA in June. In the UK, Suits airs on Tuesdays at 9pm on Dave.
> Suits renewed for second season by USA
Watch a video teaser for Suits season two below: