Lacy was born in Greenfield, Massachusetts. He grew up in Pittsford, Vermont, where he attended Otter Valley Union High School and Patricia A. Hannaford Career Center's Addison Repertory Theater pre-professional program. There, he took vocational theater classes and embarked in acting roles. In 2008, Lacy graduated from the University of North Carolina School of the Arts (UNCSA) in Winston-Salem. After graduation, he worked odd jobs in the state of New York. He worked as a gym receptionist, a bar-back at a club and a waiter, while going to auditions during the day, until being cast in the role of Casey in Better with You.

Lacy acted in high school and performed on professional stages in the productions of A Midsummer Night's Dream as Demetrius (in Hartford Stage's production), and Much Ado About Nothing as Conrad (in the Oberon Theater Ensemble's production). Lacy played brief roles in a few episodes of Guiding Light before its cancellation. In 2010, he had a lead role in the Columbia thesis film C'est moi."

From 2010 to 2011, Lacy starred as Casey in the ABC sitcom Better with You. He starred as Pete Miller, or "Plop", in the ninth and last season of The Office. His next role is in the independent sports comedy Balls Out, where he plays the lead Caleb Fuller who leads an intramural football team. In 2014, he starred in the comedy-drama film Obvious Child opposite with Jenny Slate.[4] He also appeared in the HBO comedy Girls as Fran, a love interest of Lena Dunham's protagonist Hannah. Lacey starred opposite Rooney Mara in Carol (2015), as Richard, her character's boyfriend.

Actors, Entertainment Industry, Television Actor, Movie Actor, Entertainers, Celebrity Acting, Television & Film, Comedy, Comedians,