Blumenkrantz made his Broadway debut during the original run of Into the Woods, as understudy and later replacement as Jack and also understudying Rapunzel's Prince and the steward. He appeared in revivals including 1989's Threepenny Opera (Filch), 1994's Damn Yankees (Smokey), and 1995's How to Succeed in Business Without Really Trying (Bud Frump). In original musicals, he was Charley and others in A Class Act (with Lonny Price) and Daryl Ames in Steve Martin's Bright Star. He played Simeon in the direct-to-video version of Joseph and the Amazing Technicolor Dreamcoat (with Donny Osmond and Richard Attenborough) and Beadle Bamford in the 2014 Live from Lincoln Center production of Sweeney Todd.
On television, Blumenkrantz recurred on The Detour and The Simple Life (with Florence Stanley) and has had guest roles on 30 Rock, various Law & Order series, Will & Grace, The Good Wife, Ugly Betty, and Caroline in the City. Films include The Big Sick, Amos & Andrew, The Thirteenth Floor, and the animated feature Anastasia (ensemble vocals).
As a composer, Blumenkrantz has written songs recorded by Audra McDonald and others and contributed songs to the Broadway musical Urban Cowboy (sharing in a Tony Award nomination).