Williams was born in Westchester County, New York and was raised in Yonkers, New York. His mother, Angela Williams, is a singer and songwriter, and his father, Le’Roy Williams, is a police sergeant. He has two younger brothers; Tyrel Jackson Williams and Tylen Jacob Williams, who are also both actors, with Tyrel starring on the Disney XD series, Lab Rats as Leo Dooley and Tylen starring on Instant Mom as James Phillips. Williams had also appeared on Lab Rats, portraying his brother's character's future self and Instant Mom as his younger brother family cousin Jamal.
Williams began his acting career at age four. He later starred in Little Bill as the voice of Bobby, briefly replacing Devon Malik Beckford in 2000, and played himself (or an eponymous character, "Tyler") on the children's show Sesame Street from 2000 to 2005. He rose to fame in 2005 by playing the main character in the hit series Everybody Hates Chris, which finished in 2009. He won a Young Artist Award in 2007 for his work on the show. He has also been a guest star in Two for the Money, Law & Order: Special Victims Unit, and the show Hi-Jinks. In late 2009, Williams appeared in the second season of True Jackson, VP as True's love interest Justin "Lil' Shakespeare" Weber in the two-part episode "Flirting with Fame".
In 2012, Williams got the role of Owen in the series Go On. He also played the lead role of Cyrus DeBarge in the Disney Channel Original Movie Let It Shine alongside Coco Jones, Trevor Jackson, and Brandon Mychal Smith. Williams was also featured on nine songs on the film's soundtrack, showing off his rapping skills. The movie premiered on June 15, 2012, and his songs "Don't Run Away", "Me and You", "Guardian Angel", "Let It Shine", and "Moment of Truth" all received airplay on Radio Disney. The videos were also played frequently on the Disney Channel.
In 2014 Williams starred in Justin Simien's 2014 independent film Dear White People as Lionel Higgins.
In 2014, Williams was cast as the recurring character Noah on the television series The Walking Dead.
In 2016, Williams played Russ "Monty" Montgomery in the Criminal Minds spin-off Criminal Minds: Beyond
- Little Bill
- Sesame Street
- Late Night with Conan O'Brien
- Saturday Night Live
- Everybody Hates Chris
- The Ant Bully
- 2007 Kids' Choice Awards
- True Jackson, VP
- Batman: The Brave and the Bold
- Tyler Perry Presents Peeple
- Key & Peele
- Muppets Most Wanted
- Dear White People
- The Walking Dead
- He is the second The Walking Dead cast member to be part of Whiskey Cavalier. The first being Lauren Cohan.