Hermann was born in New York City to German parents and moved to Germany when he was two months old. He lived in Germany until he was 10 and did not learn English until he returned to the United States.[3] He attended Yale University.[4] After college, he taught high school English through Teach For America.[5]
He has made appearances in several commercials, such as the anti-tobacco "Fair Enough" ads, and has been the face for Persil ProClean detergent since the late 2010s.[6]
Hermann was in the Broadway premiere of Eric Bogosian's Talk Radio, starring Liev Schreiber, and featuring fellow Law & Order: Special Victims Unit cast member Stephanie March.[8] It began performances on February 15, 2007, in preparation for a March 11 opening; its final Broadway performance was on June 24, 2007.[9][10]
He also guested on 30 Rock during its first season and starred in ABC's mid-season replacement series Cashmere Mafia as Davis Draper. In 2011, he appeared in the Broadway play War Horse, and made occasional appearances as Erin Reagan's ex-husband John "Jack" Boyle on Blue Bloods.[11][12][13]
From 2015 to 2021, he starred in Younger.[14] In March 2018, HarperCollins published Hermann's children's book If the S in Moose Comes Loose.[15] He was a guest actor in season 2 of And Just Like That....
^Willis, John; Monush, Barry (1 May 2010). "United 93". Screen World 2007. Vol. 58. Hal Leonard Corporation. p. 44. ISBN978-1557837295. Retrieved 25 August 2018.
^"Cast". Talk Radio on Broadway. Archived from the original on 8 February 2007. Retrieved 18 July 2021.