Born Mary Margaret Hahn January 22, 1937 in Missouri, Mishkin did not begin her theatrical career until the death of her husband, carpet manufacturer Ralph Mishkin, in 1993, when she was nearly 60 years old. She produced Trish Vradenburg's The Apple Doesn't Fall..., about Vradenburg's time taking care of her mother with Alzheimer's, at Los Angeles' Tiffany Theatre before bringing it to Broadway's Lyceum Theatre in 1996, Mishkin's Broadway debut.
Directed by Star Trek star Leonard Nimoy, the production would turn out to be short lived, playing just 19 previews and one performance, but Mishkin was undeterred going on to shepherd 31 Broadway shows, via producing or investing, over her career. Among the notable productions Mishkin helped bring to the Main Stem are The Beauty Queen of Leenane, It Ain't Nothin' But the Blues, A Moon for the Misbegotten, the 2000 revivals of A Moon for the Misbegotten and The Music Man, Dirty Blonde, A Class Act, Urban Cowboy, Little Women, Dirty Rotten Scoundrels, Chita Rivera: A Dancer's Life, Passing Strange, the Daniel Radcliffe-led Equus revival, Superior Donuts, End of the Rainbow, and Hands on a Hardbody.
Mishkin would have her greatest successes with the Broadway run of Dame Edna: The Royal Tour, for which she served as a lead producer, and 2010 Best Musical Tony winner Memphis, produced in association with Mishkin. Both productions won Mishkin Tony Awards, with Dame Edna being awarded a Special Tony Award in 2000.
Beyond Broadway, Mishkin was also a fixture in the commercial Off-Broadway scene, serving as a producer or associate producer on 12 productions and winning a 1998 Lucille Lortel Award for Gross Indecency: The Trials of Oscar Wilde. She also worked on a handful of theatre-related film projects, including a documentary about Broadway's Passing Strange and the 2001 filmed concert of Sweeney Todd: The Demon Barber of Fleet Street, starring George Hearn and Patti LuPone. The latter, for which Mishkin served as executive producer, won her a 2002 Primetime Emmy Award for Outstanding Classical Music-Dance Program.
Mishkin is survived by sisters Julie Kahle and Dixie May, stepson Steve Mishkin, and five step-grandchildren.