Born and raised in Pennsylvania, Groff made his Broadway debut in 2005 as a swing and understudy in the musical In My Life. A year later, he had his breakout role as Melchior Gabor in the teen rock musical Spring Awakening. Groff was nominated for a Tony Award for Best Actor in a Musical and received the Theatre World Award for Outstanding Debut Performance.
In summer 2008, Groff played Claude in Hair at Shakespeare in the Park. This was followed by two Off-Broadway plays by Craig Lucas: Prayer for My Enemy, in which he played a closeted gay solder serving in Iraq, and The Singing Forest, alongside Olympia Dukakis. Groff received an Obie Award for both performances. He returned to Shakespeare in the Park as Dionysus in The Bacchae.
Groff made his West End debut in 2010 in Deathtrap and in 2015, took over the role of King George III in the Off-Broadway production of Hamilton, which he reprised for the Broadway premiere. He was nominated for a Tony for Best Featured Actor in a Musical. In 2019, he originated the role of Seymour in the long-running Off-Broadway revival of Little Shop of Horrors.
On screen, Groff played Jesse St. James in Glee opposite his Spring Awakening co-star Lea Michele and took the lead role of Patrick in Looking, HBO’s first series to be centred around gay men. He voiced iceman Kristoff and his reindeer Sven in Disney’s Frozen and Frozen II. In 2024, he is appearing in a guest role in the science fiction TV series Doctor Who.