He originated the role of Georg in the Broadway musical Spring Awakening, and has since appeared in films such as Hamlet 2 (2008), Taking Woodstock (2009), Cavemen (2013), and 21 & Over (2013).

Astin was born in New York City, the son of Meryl and Barry Lipstein, a garment industry executive.

[6][7] Growing up in New City, New York, he graduated from Clarkstown High School North and attended Stagedoor Manor performing arts summer camp.

[8][9] Lipstein says that when he was 15, his agent suggested he use his middle name, Astin, instead of his surname as his stage last name to be "less specific to one thing" and that he is not embarrassed or ashamed of his decision.

[16][17] In 2010, Astin took on the role of Mark Cohen in a production of Rent, directed by Neil Patrick Harris, at the Hollywood Bowl.

[18] Also in 2010, he joined the cast of the Jere Burns sitcom Strange Brew on Fox, which like Ace in the Hole was not picked up.

In March 2022, it was announced that he would have a recurring role in the eighteenth season of the ABC medical drama Grey's Anatomy as Todd Eames.