Shortly before graduating from Carnegie Mellon University, Hilty auditioned for the hit musical Wicked. She moved to New York City after graduating and, in August 2004, she made her Broadway debut in the show as the standby for Galinda, before taking over the lead role from Jennifer Laura Thompson on May 31, 2005. After playing the role for a year, Hilty ended her run on May 28, 2006 and was succeeded by Kate Reinders.
She then reprised the role on the first national tour of the show from September through December 2006, replacing Kendra Kassebaum. She was succeeded by Christina DeCicco. Soon after, she originated the role in the Los Angeles sit-down production, which began previews on February 10, 2007 and opened February 21. Hilty left the production on May 18, 2008, and was replaced by Erin Mackey, only to return on October 31, 2008 to close the production, which played its final performance January 11, 2009.
Hilty starred in a musical called Vanities during its premiere engagement at the Mountain View Center for the Performing Arts in Mountain View, California. In addition to her stage work, Hilty has made guest appearances on various television shows including The Closer, The Suite Life of Zack and Cody, Ugly Betty, CSI: Crime Scene Investigation, Desperate Housewives, and Shark. She can also be heard as the singing voice of Snow White in the animated feature film Shrek the Third.
In fall 2008 Hilty joined Emmy Award-winning The West Wing star Allison Janney, fellow Wicked alum Stephanie J. Block, and Broadway veteran Marc Kudisch in the new musical adaption of the 1980 film 9 to 5. The production was directed by Joe Mantello, director of Wicked, with a pre-Broadway tryout run at the Ahmanson Theatre in Los Angeles, which opened on September 9, 2008. Hilty had participated in workshops and readings developing and originating the character of Doralee for the musical. Her character, executive secretary Doralee Rhodes, the role played by Dolly Parton in the film. Parton is the composer and lyricist of the musical. The musical began preview performances on Broadway at the Marquis Theatre on April 7, 2009 with an official opening on April 30, 2009. The show ended its Broadway run on September 6, 2009. For this role Hilty was nominated for the Outer Critics Circle Award for Outstanding Actress in a Musical, the Drama League Award for Distinguished performance, and the Drama Desk Award for Outstanding Actress in a Musical. In late 2008, Scott Alan's album Keys was released, featuring Hilty as one of the vocalists. She is featured on the song "The Dance", it being her first vocal recording and release.
In 2009, Hilty appeared in an episode of CSI: Crime Scene Investigation entitled "Deep Fried & Minty Fresh", where she played a fast food manager helping out with a murder at Choozy's Chicken. She also appeared in two episodes of Desperate Housewives where she played the other woman to Carlos' boss. Hilty also lent her talents in Rated RSO: The Music and Lyrics of Ryan Scott Oliver at The Boston Court Performing Arts Center in December 2009, alongside Lesli Margherita, Steve Kazee, Morgan Karr, Natalie Weiss, among others. Hilty also branched off into a coffee and tea product line.
Along with her former Wicked co-star Shoshana Bean, Hilty began performing a variety show together called The Meg an' Sho Show. They often perform a "Wicked swap", in which Bean sings a medley of Glinda's songs and Hilty sings Elphaba's. She also continued her television work with appearances in the hit Disney Channel shows The Suite Life of Zack & Cody and Phineas and Ferb.
In 2010 Hilty confirmed that she will be voicing the character of the China Princess in the upcoming animated feature Dorothy of Oz, and she appeared as the "Heckler" in an episode of Louis CK's comedy Louie on FX.
In 2011 it was confirmed that Hilty would star in the NBC musical television series Smash, also starring Debra Messing, Katharine McPhee, Christian Borle, Anjelica Houston, and Brian d'Arcy James. The show was officially picked up on May 11, 2011 and made its series premiere on February 6, 2012.
In May 2012 Hilty appeared in Gentlemen Prefer Blondes, as a part of the Encores! program. She appeared as Lorelei Lee alongside such performers as Brennan Brown, Simon Jones and Rachel York. Hilty received rave reviews for her performance, with the New York Times rating her performance higher than those of Carol Channing and Marilyn Monroe.