He has had roles on HBO's Vinyl, NBC's 30 Rock, Showtime's The Big C, and ABC's Ugly Betty.

He is the author of The New York Times bestselling YA book Dear Evan Hansen: The Novel and the adult novel The Reminders.

[6] While attending Rutgers University, Emmich performed with various bands, including Awake Asleep and Ben Trovato.

After graduating from Rutgers in 2001 with a degree in American Studies, Emmich recorded an independent EP entitled The 15 Minute Relationship.

The video was shot at his alma mater Rutgers University in New Brunswick, and at the night club The Saint in Asbury Park, NJ.

The video appeared on MTV's Total Request Live, making him the first unsigned artist to be featured on the show.

In 2015, Emmich began a side project called The Good Names Are Taken and released a self-titled 6-song EP.

"[15] Emmich has been influenced by a wide range of musicians including Nirvana, Smashing Pumpkins, Pearl Jam, The Beatles, Wilco, Björk, Radiohead, R.E.M., Bright Eyes,[16] Nada Surf[17] and Paul Westerberg.

[19][20] In the summer of 2008, he shot his first film, playing the lead role in the independent feature Fighting Fish.

[21] In 2014 he was hired by United Airlines for their television ad campaign "your gateway to the world", created by McGarryBowen in New York.

Emmich's debut novel, The Reminders, was published by Little Brown in the US and Canada in 2017[24] as well as in the U.K. (Picador), Denmark (Politikens), China (Horizon), France (Mosaic), Israel (Kinneret), Italy (Piemme), Germany (Droemer), Brazil (Intrinseca), and Holland (Ambo Anthos).

In the National Book Review, "The Reminders" was deemed "A charming debut novel....Like Nick Hornby, Emmich has a knack for avoiding the treacly and saccharine while finding magic in unlikely relationships."

[25] In 2018, Emmich adapted Steven Levenson and Pasek and Paul's Broadway musical Dear Evan Hansen into a young adult novel.