He is known for his roles as Dylan Baxter in Evan Almighty (2007), Chip Dove in Jennifer's Body (2009), "Young Neil" Nordegraf in Scott Pilgrim vs. the World (2010) and Scott Pilgrim Takes Off (2023), Brad Hayes in The Perks of Being a Wallflower (2012), serial killer Adam "Balloon Man" Kemper in Elementary (2012), Peter Newmans in The Late Bloomer (2016), and Shane in Girlboss (2017).

Also in 2009, Simmons starred in the black comedy horror film Jennifer's Body as Chip Dove, the boyfriend of Amanda Seyfried's character, Anita "Needy" Lesnicki.

[1] In 2010, he starred in the comedy film Scott Pilgrim vs. the World, portraying Young Neil, a 20-year-old bass guitarist and fan of the fictional band Sex Bob-omb.

[3] Also in 2012, Simmons co-starred as the closeted quarterback Brad Hayes, alongside Logan Lerman, Emma Watson, and Ezra Miller, in the teen drama The Perks of Being a Wallflower.

[5] That same year, Simmons joined the comedy film Frank and Cindy as GJ Erchternkamp, alongside Rene Russo and Oliver Platt.