As a junior, he continued to start and became a team leader off the field. He finished third in the Atlantic Coast Conference in tackles for loss. During the 2016 Independence Bowl, Chubb sacked Vanderbilt quarterback Kyle Shurmur, which made a favorable impression on Kyle's father Pat Shurmur, who scouted Chubb extensively in early 2018.
The Denver Broncos selected Chubb in the first round with the fifth overall pick in the 2018 NFL Draft. Chubb was the first defensive end drafted in 2018.
On June 21, 2018, the Denver Broncos signed Chubb to a fully guaranteed four-year, $27.27 million contract that includes a signing bonus of $17.91 million.
He made his professional regular season debut and first career start in the Denver Broncos’ season-opener against the Seattle Seahawks and recorded three combined tackles and was credited with half a sack during a 27–24 victory. He made his first career sack with teammate Darian Stewart on Seahawks’ quarterback Russell Wilson for a six-yard loss during the first quarter. In Week 3, he recorded two solo tackles and made his first career solo sack on Ravens’ quarterback Joe Flacco during a 27–14 loss at the Baltimore Ravens. On October 14, 2018, Chubb recorded five combined tackles and made a season-high three sacks on quarterback Jared Goff as the Broncos lost 23–20 against the Los Angeles Rams. The following week, he made three solo tackles, two sacks, and made one forced fumble by quarterback Josh Rosen during a 45–10 win at the Arizona Cardinals in Week 7. For his efforts, Chubb was named NFL Defensive Rookie of the Month for October. In Week 11, he collected season-high seven combined tackles and made one sack during a 23–22 win at the Los Angeles Chargers. He started in all 16 games in 2018 and recorded 60 combined tackles (41 solo), 12 sacks, two forced fumbles, and one pass deflection. He received an overall grade of 68.9 from Pro Football Focus, which ranked 48th among all qualifying edge rushers in 2018. He was ranked 82nd by his fellow players on the NFL Top 100 Players of 2019.