Sieber was born in St. Paul, Minnesota, to Fred and Caron Sieber. He is the middle child of three. Mike, his older brother, was a swimmer, and his younger brother, Marc, was in drama alongside him. He is a 1988 graduate of Forest Lake Area High School in Forest Lake, Minnesota, and was inducted into the Forest Lake Schools Hall of Fame in June 2011. After graduating, Sieber went to New York City to study at the American Musical and Dramatic Academy.[1]
On January 31, 2014, it was announced that Sieber would be joining the company of Matilda the Musical on Broadway as Miss Trunchbull starting performances on March 18.[3] However, due to a hand injury sustained in rehearsals, he did not start performances until April 18.[4]
In 2016, Sieber joined the cast of The Prom as Trent Oliver in the out-of-town tryout at Atlanta’s Alliance Theater, and continued in the role at Broadway’s Longacre Theater from October 2018 to August 11, 2019.[5][6]
On March 4, 2024, it was announced that Sieber would join the cast of Death Becomes Her as Ernest Menville in its preview run at Chicago's Cadillac Palace Theatre, Starting performances on April 30, 2024.[7]
While It's All Relative was being produced, Sieber came out as gay and said that he was happily partnered to actor and chef Kevin Burrows.[10] They married on November 24, 2011, in New York City.[11] The couple live on an island on Lake Tamarack in the Stockholm area of Hardyston Township, New Jersey.[12][13]
Sieber is involved with Broadway Cares/Equity Fights AIDS (BC/EFA) and has appeared in several of its Broadway Cares revues, among other events the charity produces. He teaches classes on drama and performance.
^"Artist activists will come together to support county Democrats". New Jersey Herald. May 7, 2017. Archived from the original on 2020-08-06. Retrieved January 13, 2018. Billeisen, who will emcee the evening, will be joined by Seth Danner and Christopher Sieber, Stockholm resident and two-time Tony nominee for Monty Python's 'Spamalot' and 'Shrek The Musical,' along with other contributing performers.