Smagula made his professional acting debut at age 20 in the Paper Mill Playhouse production of Man of La Mancha. He also appeared in the American premiere of Children of Eden, also at Paper Mill Playhouse. Smagula also sings on that production's cast album.
Smagula appeared in the ensemble and performed the role of Beadle Bamford in Sweeney Todd: The Demon Barber of Fleet Street at the Ahamanson Theater with Kelsey Grammer and Christine Baranski and also played the Beadle in the Signature Theater production in Arlington, VA, which starred Norm Lewis.
Smagula made his Broadway debut at age 24 in the ensemble of The Full Monty (2000). He performed the principal role of Dave Bukatinsky over 3 dozen times, opposite both Patrick Wilson and Will Chase. In 2002, he appeared in the Broadway revival of Man of La Mancha starring Brian Stokes Mitchell.
Smagula understudied Ubaldo Piangi on the Second National Tour of The Phantom of the Opera and later played the role on the Third National tour. He also would understudy the role on Broadway for one year.[4]
In 2005, Smagula appeared as Sal Iacuzzo on HBO's The Sopranos. He also appeared in the film The Island, directed by Michael Bay and The Producers movie musical.
In 2008, Smagula starred as Rocky in the Encores! production of Damn Yankees! starring Sean Hayes and Jane Krakowski at the New York City Center. Ben Brantley of the New York Times said Smagula "harmonizes sweetly" on the iconic song "Heart."[5]
Smagula appeared in Manhattan Theatre Club's production of To Be or Not To Be at the Friedman Theater on Broadway, directed by Casey Nicholaw.
He also played a 10-week stint as Chef Louis in Disney's The Little Mermaid on Broadway[6]
In 2010, Smagula joined the Broadway company of Billy Elliot, where he performed the principal role of George over 50 times. He also appeared in the film Step Up 3D in 2010.
From 2011 to 2016, Smagula appeared in television shows including Hot in Cleveland, Grey's Anatomy, Jessie, Betty White's Off Their Rockers, Parks and Recreation, Sam and Cat, Brooklyn Nine-Nine, Rizzoli and Isles, Community, and Bones.
In 2017, Smagula played John Woodburn in the film Rebel in the Rye, written and directed by Danny Strong and starring Kevin Spacey and Nicholas Hoult.[7]
From 2019 to 2020, Smagula played Monsieur Thénardier in the national tour of Les Misérables.[8]
In 2022, he played Harry the Horse in Guys and Dolls at The Eisenhower Theater.[8]
In 2023, he played the dual role of Mr./Billy Webster in Stephen Sondheim and James Lapine's Sunday in the Park with George at the Pasadena Playhouse. He also played Sir Bedevere in the Kennedy Center production of Spamalot and reprised the role in the Broadway revival at the St. James Theatre.[8]