[5] Williams struggled in training camp adjusting to the team's offense, but by the end of the preseason, he had supplanted Dwayne Harris as the third wide receiver.

Williams again struggled at the start of the regular season with his route running and dropped passes, until the fourth game against the San Diego Chargers, where he started in place of an injured Miles Austin and registered seven receptions for 71 yards, but also had a critical fumble trying to extend for a touchdown in the last minutes of the 30–21 road loss.

[7] By Week 8 against the Detroit Lions, Williams set a Cowboys franchise record for rookies, with a touchdown in his fourth consecutive game.

[11] During the first playoff game of the Cowboys’ season and his career, Williams once again solidified his status as a playmaker by registering three receptions for 92 yards, while scoring two critical touchdowns against the Detroit Lions and their No.

Williams had a career-game statistically in the regular-season finale against the Washington Redskins, making eight receptions for 173 yards in a 34–23 loss with Kellen Moore as the starting quarterback.

[20] In the divisional round against the Green Bay Packers, Williams caught four passes for 68 yards as the Cowboys narrowly lost 31–34.

[22] During a Week 9 28–17 victory over the Kansas City Chiefs, Williams had his best game of the season, catching nine passes for 141 yards.

[31] The Ottawa Redblacks of the Canadian Football League (CFL) announced that Williams had signed with the team on September 13, 2021,[32] but he was released on October 8, 2021.

He made his debut against the Bored Ape FC on March 16, recording a completed two-point conversion and a nine-yard reception.

[35] On May 19, 2018, Williams was arrested in Frisco, Texas, on suspicion of misdemeanor public intoxication after his car was found crashed into a light pole.

[36] On August 1, 2018, public intoxication charges were dismissed after Williams completed a state-mandated Alcohol Awareness Education course.