[4] On March 24, 2014, Hitchens opted to participate at Iowa's pro day, along with C. J. Fiedorowicz, Christian Kirksey, James Morris, and nine other prospects.

[5] At the conclusion of the pre-draft process, Hitchens was projected to be a seventh round pick or priority undrafted free agent by the majority of NFL draft experts and scouts.

Jones also stated they planned on selecting Hitchens in the fourth round ahead of time and his speed, athleticism, and tackling ability were key factors.

[11] He began organized team activities taking reps with the first-team defense, but was soon moved to the backup middle linebacker after Justin Durant returned from a hamstring injury.

[13] Head coach Jason Garrett named Hitchens the back up middle linebacker to McClain to begin the 2014 season.

[11] He made his professional regular season debut in the Cowboys' season-opener against the San Francisco 49ers and assisted on one tackle in the 28–17 loss.

[14] The following week, Hitchens earned his first career start at weakside linebacker and recorded two combined tackles during a 26–10 victory at the Tennessee Titans.

[15] During a Week 3 matchup at the St. Louis Rams, Hitchens collected a season-high 13 combined tackles and deflected a pass in Dallas' 34–31 victory.

Head coach Jason Garrett named Hitchens the weakside linebacker for the remainder of the season after Justin Durant was placed on injured/reserve after tearing his biceps in the Cowboys' 20–17 overtime loss to the Washington Redskins on Monday Night Football.

In Week 2, Hitchens recorded five combined tackles and made his first career sack on Philadelphia Eagles quarterback Sam Bradford during a 20–10 victory.

On December 19, 2015, Hitchens started at middle linebacker in place of McClain who suffered an injury and collected ten combined tackles during a 19–16 loss to the New York Jets.

[23] Hitchens began training camp competing with Kyle Wilber and Damien Wilson for the role as the strongside linebacker.

[24] He took over the role as the Cowboys' starting middle linebacker after McClain was dealt a ten-game suspension after violating the performance-enhancing drugs policy.

On December 1, 2016, Hitchens recorded a season-high ten combined tackles, deflected a pass, and sacked Minnesota Vikings quarterback Sam Bradford, as the Cowboys won 17–15.

On January 15, 2017, Hitchens started his first career playoff game and collected seven combined tackles in a 34–31 loss at the Packers in the NFC Divisional Round.

The Proven Performance Escalator was added to the rookie wage scale as a part of the collective bargaining agreement in 2011 and applies to players who were drafted in the third to seventh round.

Hitchens was slated to start the season at middle linebacker, but suffered a tibial plateau fracture in the Cowboys' final preseason game against the Oakland Raiders.

He was heavily linked to the Colts due to his experience under defensive coordinator Matt Eberflus who was his linebacker coach with the Dallas Cowboys.

Head coach Andy Reid named Hitchens and Reggie Ragland the starting inside linebackers to begin the regular season.

Hitchens finished the 2018 NFL season with a career-high 135 combined tackles (81 solo) and forced one fumble in 15 games and 15 starts.