McCartan began his career with a minor part in the
stage version of ''
Disney's High School Musical'' in 2007. In 2011 he starred in the titular role in Minnesota's first regional production of
The Phantom of the Opera. That same year, he won Best Performance by an Actor at the
Jimmy Awards, given out by
The Broadway League to the top performers in high school musical productions. McCartan originated the role of Jason Dean in the original
Off-Broadway cast of the musical
Heathers, which ran from March through August 2014. He previously played the role in the 2013 world premiere of the musical in Los Angeles. In July 2013, McCartan began playing the recurring role of Diggie on the
Disney Channel comedy
Liv and Maddie. He was in the show until the finale, which aired on March 24, 2017. In 2015, he starred in the direct-to-video film ''
R.L. Stine's Monsterville: Cabinet of Souls''. In May 2015,
Dove Cameron announced that she and McCartan were officially forming a pop duo and would be releasing their first original song. In September 2015, they announced their group's name would be
The Girl and the Dreamcatcher, and their first video was released in October 2015. The pair broke up in October 2016. On September 11, 2018, McCartan made his
Broadway debut as
Fiyero in the musical
Wicked. He remained with the show until May 12, 2019, where
Jessica Vosk also played her final performance as Elphaba. In mid-2018 he originated the lead role of Eddie Corbin in the new musical
Mutt House at the Kirk Douglas Theatre, and in August 2019 he played Lt. Cable in
South Pacific at the
Aspen Music Festival. In 2019, he starred in the role of Mac in the
Roundabout Theatre Company's new musical
Scotland PA. In November 2019 he made his solo show debut at
Feinstein's/54 Below. In April 2020, he hosted the
Broadway Cares/Equity Fights AIDS viewing of 25 Years of
Disney Broadway. He joined the cast of
Frozen on Broadway as
Hans in February 2020 opposite
McKenzie Kurtz as Anna and
Ciara Renée as Elsa. However, due to the ongoing
COVID-19 pandemic, all Broadway theatres were closed in March. Disney later announced, on May 14, 2020, that
Frozen would not reopen after the lifting of the lockdown. During 2022, he played Hans in the Broadway National tour of
Frozen for two runs, with his final performance being September 4, 2022. His first run would reunite him with Kurtz, his Broadway Anna. In October 2022, McCartan was cast as Kyle Reed in the spin-off of
Supernatural,
The Winchesters. In June 2023, McCartan starred as Tony in a production of
West Side Story at the
Lyric Opera of Chicago. In November 2023, McCartan starred as Cletis in the Off-Broadway production of
Lone Star. In September 2024, he took on
the titular role in
Randy Newman's Faust at The Soraya in Los Angeles, California. He starred opposite
Reeve Carney,
Javier Munoz and
Veronica Swift. However, it was later announced McCartan would be replaced by
Kyle Selig, and instead join the cast of
The Great Gatsby on Broadway beginning in January 2025 replacing
Jeremy Jordan in the title role. He's performed opposite
Eva Noblezada,
Sarah Hyland, and
Aisha Jackson as Daisy. In May 2026, he’ll star in
West Side Story as Tony as a part of the
Washington National Opera at the
Lyric Baltimore and
Music Center at Strathmore. == Personal life ==