She made her Broadway debut as Johanna in the 2005 revival of Sweeney Todd,^[9] Described as a "sweet-voiced soprano who...plays the cello beautifully" by The New York Times, she received the Independent Reviewers of New England Award Best Supporting Actress, while performing on the first national tour, and was named as one of the "30 Under 30" featured on Broadwayspace.com.

Hilton Als, featured Molina in the "Critic's Notebook" of The New Yorker, saying "Most of the kudos for the current revival of Stephen Sondheim’s 1979 musical, “Sweeney Todd,” have gone to Patti LuPone and Michael Cerveris. But Lauren Molina also deserves her share. Making her Broadway début as Johanna, Sweeney's long-lost daughter, Molina projects such sweet confusion, mental terror, and consistent interiority that she exposes the ways in which seasoned pros like LuPone and Cerveris play to the audience from time to time. Molina is a newcomer—she only recently graduated from college—but she taps into Johanna with an all-consuming honesty and range. Given her unconventional good looks and delicacy of frame, filmmakers in the sixties and seventies like Lumet, Coppola, and others would have snatched Molina up as quickly as they did the late, great Elizabeth Hartman, who conveyed an effect similar to Molina's in “The Group,” “You’re a Big Boy Now,” and “The Beguiled” —that of a highly intelligent actress in love with being someone other than herself."^[10]

In 2008, she originated the role of Regina/Candi in the 80's rock musical Rock of Ages off-Broadway at New World Stages. She played the same role on Broadway from April 2009 – August 2010. She won a Helen Hayes Award for the role of Cunegonde in Candide in a 2010–11 production that was newly adapted and directed by Mary Zimmerman at the Goodman Theatre, Chicago, the Shakespeare Theatre, Washington D.C., and The Huntington Theatre in Boston.

She was also a part of the Drama League Nominated, two person revival of Stephen Sondheim's Marry Me A Little with Jason Tam, off-Broadway at the Clurman Theatre with Keen Company. The cast album was recorded by Ghostlight/Sh-K-Boom and released November 2013.

In 2017, Lauren originated the role of Bella Rose in the Drama Desk Award-Winning Off-Broadway show Desperate Measures. She received the Lucille Lortel Award for Outstanding Actress in a Musical and Outer Critics Circle for Best Supporting Actress nominations. Broadway world said, "...Lauren Molina, as Bella, gives one of those uproarious performances that used to make people stay home on Saturday nights to see on "The Carol Burnett Show." She mugs unmercifully, belts out a sassy strip number and, [has an] homage to Groucho and Harpo's classic mirror scene in "Duck Soup."^[11]

The show began at the York Theatre then transferred to New World Stages. She recorded the original cast album released by Sony Masterworks.^[12]

She is a co-conceiver of the new actor-musician revisal of “You're a Good Man, Charlie Brown” which debuted at the Cincinnati Playhouse in April 2019. She also played the role of Lucy and was described by the Cincinnati Enquirer as "a powerhouse of a performer".^[13] Critics raved that “The production at Cincinnati Playhouse in the Park may be the best we are likely to ever encounter, thanks to the inventiveness of the presentation and the talented cast.” ^[14]

She has been seen regionally as Squeaky Fromme in Assassins directed by James Bundy (Yale Rep), Eileen in Wonderful Town directed by Mary Zimmerman (Goodman Theatre), Countess in A Little Night Music directed by Peter DuBois (Huntington Theatre Company), Audrey in Little Shop of Horrors directed by Amanda Dehnert (Cleveland Play House), Janet in The Rocky Horror Show directed by Hunter Foster (Bucks County Playhouse), The World Premiere of Meet Me In Saint Louis: A Radio Play directed by Gordon Greenberg (Bucks County Playhouse) and It's a Wonderful Life: A Radio Play directed by Gordon Greenberg (Bucks County Playhouse).^[15]

Other roles she's originated include: Megan in the world premiere musical, NOBODY LOVES YOU, at both The Old Globe and off-Broadway at Second Stage in 2013; Miss Jones 1 in TEN CENTS A DANCE, with Donna McKechnie and Malcolm Gets at the Williamstown Theatre Festival (This original musical, created by John Doyle, utilized actor/singer/musicians, Lauren playing cello, bass, guitar, ukulele and saxophone, and expressed the story thru the music of Rodgers and Hart); Liza in THE FORTRESS OF SOLITUDE by Itamar Moses and Michael Friedman.

She was a featured singer at "The Ladies Who Sing Sondheim" concert with Barbara Cook and Patti Lupone at the Westport Playhouse. She also was a soloist at the "Tribute for Angela Lansbury" with Tyne Daly and Christine Ebersole held at the Bucks County Playhouse. In addition, she was a back-up singer for Sarah Brightman on her La Luna tour.