The former Dawson Creek star plays a 30-something woman in the Dead Accounts production, whose brother returns from New York after conducting some dodgy business deals there.
Katie seemed to be very pleased with her opening night, as she grinned for photographers on her way to the after party.
She said of her gutsy character:
"What I really loved about this character was she's strong underneath it all. I like her values, I like that she's trying to figure it all out and really cares for her family."
The play marked Katie's first return to Broadway since appearing in the 2008 production of All My Sons.
The mother-of-one wore a striking floral dress and loose curls as she posed for the cameras at the after party.
Katie’s parents, Martin and Kathleen, were also there to see her opening night at the Music Box Theatre.
However, critics’ reviews to Dead Accounts, which was written by Smash creator Theresa Rebeck, have been mixed.
The New York Times wrote: “Dead Accounts is, I think, meant to be about the inflation of the superficial in a materialistic society, and the attendant, unsatisfied craving for belief. ... But the play never follows through convincingly on any of its ideas.”
The LA Times, meanwhile wrote: "[Holmes is] charming, natural and, yes, about as fresh-faced as a moisturizer model. But there's only so much that can be done with a Rebeck play that has more topical urgency (greed, ethics and banking funny business) than dramatic finesse."
The actress had admitted to sleepless nights, worrying about reaction to the show.
"I have a hard time sleeping because I think about how serious this all is. I think about the cost of tickets," the 33-year-old admitted to The New York Times.
"I think to myself: 'You better do a good job. People are paying a lot of money.' You want to know your stuff."