Isaac's entry into professional acting began at the Area Stage Company, Miami Beach, when Artistic Director John Rodaz cast him in a play. He also acted in Miami-based City Theatre's Summer Shorts short play festival in 2000–2001. While in Miami, he played lead guitar and sang vocals for ska-punk band The Blinking Underdogs. Other band members included Nick Speck (bass), Bill Sommer (drums), Alan Mills (trombone), Keith Cooper (saxophone), and Matt LaPlant (guitar). The band enjoyed some success, opening for Green Day and The Mighty Mighty Bosstones. Isaac spent his musical years living a "straight edge" lifestyle. Isaac put music aside after being accepted into the acting program of New York's prestigious Juilliard School in 2001. While a student there, he worked on one of his first films, "All About the Benjamins" (2002). He was part of the Drama Division's Group 34 (2001–2005).