New England Patriots
Etling was drafted by the New England Patriots in the seventh round (219th overall) of the 2018 NFL Draft.
In the Patriots' first preseason game of the 2018 season, Etling completed two of five passes for 21 yards and no touchdowns. In the final preseason game, Etling went 18-32 for 157 yards with one touchdown pass and two interceptions. He also ran for 113 yards on seven carries, including an 86-yard touchdown run. Etling holds the record for longest quarterback run in Patriots preseason history.
On September 1, 2018, Etling was waived by the Patriots and was signed to the practice squad the next day. Etling won Super Bowl LIII with the Patriots when they defeated the Los Angeles Rams 13–3. He signed a reserve/future contract with the Patriots on February 5, 2019.
At the start of the 2019 season's training camp, Etling transitioned to the wide receiver position. He was waived on August 13, 2019.
Atlanta Falcons
On August 14, 2019, Etling was claimed off waivers by the Atlanta Falcons. He no longer was making the transition to wide receiver and switched back to full time quarterback. He was waived on August 31, 2019, and was signed to the practice squad the next day. On October 26, after an injury to starter Matt Ryan, Etling was promoted to the active roster as the team's backup quarterback ahead of their Week 8 matchup. He was waived on October 28, and re-signed to the practice squad. On December 30, 2019, Etling was signed to a reserve/future contract.
Etling was placed on the reserve/COVID-19 list by the Falcons on July 31, 2020 and was activated five days later. On August 17, the Falcons waived Etling.
Seattle Seahawks
On August 18, 2020, Etling was claimed off waivers by the Seattle Seahawks. On September 5, 2020, Etling was waived from the Seahawks, and signed to the team's practice squad the next day. On January 11, 2021, Etling signed a reserve/futures contract with the Seahawks. He was waived on August 1, 2021.
Minnesota Vikings
On August 2, 2021, Etling was claimed off waivers by the Minnesota Vikings. He was waived on August 23.
BC Lions
On September 10, 2021, Etling was signed by the BC Lions to their practice roster. He was waived 3 weeks later.
Seattle Seahawks (second stint)
On October 13, 2021, Etling was signed by the Seattle Seahawks to their practice squad. He was released on October 27.
Denver Broncos
On November 13, 2021, Etling was signed to the Denver Broncos practice squad due to backup Drew Lock testing positive for Covid-19. He was released three days later after Drew Lock returned.
Green Bay Packers
On December 7, 2021, Etling was signed to the Green Bay Packers practice squad in the wake of Packers backup quarterback Jordan Love being placed on the COVID-19 reserve list. He was released six days later.
Jacksonville Jaguars
On December 20, 2021, Etling was signed to the Jacksonville Jaguars practice squad.
Green Bay Packers (second stint)
On January 25, 2022, Etling signed a reserve/future contract with the Green Bay Packers.