His works often explore dark and controversial subject matter such as mental illness, grief, the underbelly of suburbia, and ethics in both psychiatry and public education.

[3][4] Prior to bringing Next to Normal to Broadway, Yorkey was affiliated with Village Theatre in Issaquah, where he began as a KIDSTAGE student and eventually progressed to a seven-year tenure as Associate Artistic Director.

[6][7][8] While at Village Theatre, Yorkey founded the KIDSTAGE Company class which teaches teens to write, direct, and perform their own musicals.

Next to Normal began as a ten-minute-long piece called Feeling Electric, which recent college graduates Yorkey and Kitt wrote as a final project for the BMI Musical Theatre Workshop at the end of the 1990s.

"[14] In 2013, Yorkey's musical with Kitt, If/Then, starring Idina Menzel, LaChanze, and Anthony Rapp, had its pre-Broadway try-out at The National Theatre in Washington, D.C.

Freaky Friday is produced by Disney Theatrical Productions, and had its World Premiere at the Signature Theatre (Arlington, Virginia) in October 2016.

Yorkey was working with Tom Kitt on a musical adaption of Magic Mike, with Roberto Aguirre-Sacasa writing the book.

[25] According to various news sources, on May 2 and 3, 2019, the creative team of Kitt, Yorkey and Aguirre-Sacasa have left the project and a private workshop that had been scheduled for the week of May 3 has been cancelled.