Jackson was selected in the fifth round of the 2012 NFL draft by the Denver Broncos, with whom he won Super Bowl 50 in 2016, in which he scored the game's first touchdown on a fumble recovery.

[8] At the conclusion of the pre-draft process, Jackson was projected to be a sixth or seventh round pick by NFL draft experts and scouts.

[12] Throughout his first training camp, Jackson competed against Robert Ayers, Derek Wolfe, Jeremy Beal, Ben Garland, Jamie Blatnick, and Jason Hunter for starting defensive end role.

[16] In the next game against the Houston Texans, he made his first career tackle on running back Arian Foster and stopped him for no gain during the third quarter of a 31–25 loss.

On January 12, 2013, Jackson played in his first NFL playoff game as the Broncos lost to the Baltimore Ravens 38–35 in overtime during the AFC Divisional Round.

Head coach John Fox named Jackson the backup defensive end behind starters Derek Wolfe and Robert Ayers to start the regular season.

[20] On September 23, 2013, Jackson recorded one tackle assist and was credited with half a sack on Oakland Raiders' quarterback Terrelle Pryor during their 37–21 victory.

[21] During a Week 5 matchup at the Dallas Cowboys, he two combined and earned his first career solo sack on quarterback Tony Romo as the Broncos won 51–48.

[23] On December 1, 2013, Jackson earned his first NFL start and made two combined tackles and forced a fumble in a 35–28 road victory against the Kansas City Chiefs.

Jackson finished his second professional season with 42 combined tackles (30 solo), six sacks, four pass deflections, and a forced fumble in 16 games and five starts.

[26] On January 12, 2014, Jackson made his first career postseason start and collected three solo tackles and a sack on San Diego Chargers' quarterback Philip Rivers in Denver's 24–17 victory in the AFC Divisional Round.

[27] After defeating the New England Patriots in the AFC Championship, the Denver Broncos played the Seattle Seahawks in Super Bowl XLVIII.

[28] Jackson started the game at defensive end and made five combined tackles and a pass deflection as the Broncos were routed by Seattle 43–8.

[33] Throughout his first training camp under new head coach Gary Kubiak, Jackson competed against Antonio Smith and Vance Walker for the starting left defensive end role.

[34] During Week 5 against the Oakland Raiders, Jackson recorded six combined tackles and sacked quarterback Derek Carr during a 16–10 road victory.

[35] Three weeks later, he collected two combined tackles, deflected a pass, and recorded the first safety of his career in a 29–10 victory over the Green Bay Packers.

During Week 3 against the Baltimore Ravens, Jackson collected two combined tackles and recorded his first sack as a Jaguar on quarterback Joe Flacco in a 19–17 loss.

[50] He joined a stout defensive line that consisted of Yannick Ngakoue, Dante Fowler, Marcell Dareus, and was headed by Calais Campbell.

[51] Jackson started in the season-opener at the Houston Texans and made three solo tackles, deflected a pass, and a sack during a 29–7 road victory.