The Post reported that Mr. Mitchell, 52, collapsed in the Mikhail Baryshnikov vehicle, Forbidden Christmas, or the Doctor and the Patient, during the second of its six-performance run. The show was stopped and a doctor in the audience attended to him. He was reportedly taken to George Washington University Hospital and later transferred to Washington Hospital Center.
The rest of the tour has been canceled. Choreographer Luis Perez stepped into the Kennedy Center run.
Mr. Mitchell was a Brooklyn native with varied Broadway credits over the past 20 years. He most recently appeared in the Broadway revival of Man of La Mancha, and had roles in Steel Pier, Chicago, Chronicle of a Death Foretold, Kiss of the Spider Woman, Man of La Mancha (1992), Aspects of Love (he was also the dance captain), Dangerous Games (he was also the fight captain), Song and Dance and Merlin.
The Post reported that Mitchell had joined the company of Forbidden Christmas six weeks ago. The show premiered at the Guthrie Theatre earlier this year.
In Forbidden Christmas, an original play by the internationally acclaimed writer, director and visual artist Rezo Gabriadze, Mr. Mitchell played an angel.
Baryshnikov Dance Foundation and David Eden Productions, Ltd. called the work "part absurdist drama, part fantasy-allegory." The five-character ensemble work featured Mikhail Baryshnikov, Jon DeVries, Gregory Mitchell, Pilar Witherspoon and Yvonne Woods.
"I remembered him from his early days with the Eliot Feld company," Baryshnikov told The Post. "He had a bright and lively personality, very outgoing. Then I saw him occasionally on Broadway and in commercials." According to The Post, Mr. Mitchell was performing a scene in which his character attempts to save the Baryshnikov character, a former sailor who has thrown himself into the sea.
"I thought he had tripped. I thought it was a joke. I couldn't believe that it would happen that way," Baryshnikov told the Post.
Mr. Mitchell also worked as a performer to help develop a new biographical show focusing on the life and career of Chita Rivera, featuring Rivera herself. They had appeared in Merlin together and both had a connection as gypsies, though they started in different decades.
Survivors include sons, Garrett, 16, and Chase, 10.
A memorial service is expected in New York City at a future date.