Cleveland Browns
The Cleveland Browns selected Mayfield with the first overall pick in the 2018 NFL draft. Mayfield signed a four-year rookie contract with the Browns on July 24, 2018, with the deal worth $32.68 million in guaranteed salary.
Mayfield played in his first NFL game in Week 3 against the New York Jets, replacing an injured Tyrod Taylor with the Browns down 14–0. Mayfield went 17 of 23, passing for 201 yards as the Browns came back and prevailed 21–17, ending their winless streak at 19 games. Mayfield became the first player since Fran Tarkenton in 1961 to come off the bench in his debut, throw for more than 200 yards, and lead his team to its first win of the season.
Mayfield started for the first time in the Browns' next game, making him the 30th starting quarterback for the Browns since their return to the NFL in 1999, in a 45–42 overtime loss to the Oakland Raiders. In Week 5, Mayfield threw for 342 passing yards and one touchdown as he earned his first victory as a Browns starter, in a 12–9 overtime win over the Baltimore Ravens. In Week 10, Mayfield led the Browns to a 28–16 victory over the Atlanta Falcons. throwing for 216 yards, three touchdowns, and a passer rating of 151.2, with no turnovers. The following week, Mayfield led the Browns to their first away win since 2015, against the Cincinnati Bengals. He completed 19 of 26 passes for 258 yards and four touchdowns. In Week 12, in a 29–13 loss to the Houston Texans, Mayfield passed for 397 yards, one touchdown, and three interceptions. Mayfield bounced back in the following game, a 26–20 victory over the Carolina Panthers, going 18 of 22 for 238 passing yards and one touchdown.
In Week 16, Mayfield completed 27 of 37 passes for 284 yards and three touchdowns with no interceptions in a 26–18 win over the Cincinnati Bengals, earning him American Football Conference (AFC) Offensive Player of the Week. He also won the Pepsi NFL Rookie of the Week fan vote for the sixth time. On December 29, Mayfield was fined $10,026 for unsportsmanlike conduct during the game. As reported by The Plain Dealer, Mayfield "pretended to expose his private parts" to Browns offensive coordinator Freddie Kitchens after throwing a touchdown to tight end Darren Fells. Kitchens later defended the gesture as an inside joke between the two. Mayfield's agent Tom Mills said they would appeal the fine. On December 30, in the regular-season finale against the Ravens' league-best defense and fellow rookie quarterback Lamar Jackson, Mayfield threw for 376 yards and three touchdowns, but his three costly interceptions — one of which came at the hands of linebacker C. J. Mosley with 1:02 left in the fourth quarter while attempting to drive the team into range of a game-winning field goal attempt — ultimately contributed to a 26–24 loss.
Nonetheless, Mayfield helped lead the Browns to finish the season at 7–8–1, their best record since 2007. He finished with 3,725 passing yards, and surpassed Peyton Manning and Russell Wilson for most touchdowns thrown in a rookie season with 27.
While Mayfield was considered by many to be the favorite for Offensive Rookie of the Year for 2018, the award was won by Giants running back Saquon Barkley. However, the Pro Football Writers of America named him the NFL Rookie of the Year. On the annual Top 100 Players list for 2019, Mayfield's peers named him the 50th best player in the league, one spot behind teammate Myles Garrett. He was named 2018 PFWA All-Rookie, the second Cleveland quarterback to receive this honor since Tim Couch in 1999.
In Week 1 against the Tennessee Titans, Mayfield threw for 285 yards and a touchdown. However, he also threw three fourth-quarter interceptions, one of which was returned by Malcolm Butler for a touchdown. The Browns lost 43–13. After the blowout loss, Mayfield said, "I just think everybody just needs to be more disciplined. I think everybody knows what the problem is. We'll see if it's just bad technique or just see what it is. Dumb penalties hurting ourself and then penalties on my part. Just dumb stuff." In Week 2 against the Jets, Mayfield finished with 325 passing yards, including a quick-attack pass to Beckham that went 89 yards for a touchdown, as the Browns won 23–3. In Week 4 against the Ravens, Mayfield threw for 342 yards, one touchdown, and one interception in the 40–25 win. Against the San Francisco 49ers, Mayfield struggled against a stout 49ers defense, completing just 8-of-22 passes for 100 yards with two interceptions as the Browns were routed 31–3.
Mayfield threw two touchdown passes in a game for the first time that year in a Week 10 victory against the Buffalo Bills, completing 26 of 38 passes for 238 yards with two TDs, including the game-winner to Rashard Higgins, as the Browns snapped a four-game losing streak with a 19–16 win. Four days later, against the Pittsburgh Steelers and former Big 12 Conference rival Mason Rudolph, Mayfield recorded his first career win against Pittsburgh, accounting for three total touchdowns (2 passing, 1 rushing), as Cleveland won 21–7. In Week 12 against the Miami Dolphins, Mayfield threw for 327 yards, three touchdowns, and one interception in the 41–24 victory. In Week 17 against the Bengals, Mayfield became the first Cleveland Browns QB to start all 16 games in a season since Tim Couch in 2001. In the game, Mayfield threw for 279 yards, three touchdowns, and three interceptions as the Browns lost 33–23. Mayfield finished the 2019 season with 3,827 passing yards, 22 touchdowns, and 21 interceptions as the Browns finished with a 6–10 record.
In Week 1 against the Ravens, Mayfield threw for 189 passing yards, a touchdown and an interception in a 38–6 loss. He bounced back in Week Two, against the Bengals, finishing with 218 passing yards, two touchdowns and an interception in the Browns' 35–30 win. In Week 6 against the Steelers, Mayfield completed 10 of 18 passes for 119 yards, with one touchdown, two interceptions and took four sacks during the 38–7 loss. Mayfield was replaced by Case Keenum in the third quarter due to aggravation of a minor rib injury he suffered in the previous week's game. In Week 7, against the Cincinnati Bengals, Mayfield struggled early, as the only one of his first five pass attempts which was caught was an interception, but later completed 22 of 23 passes for 297 yards and a career-high five touchdowns – the last one to Donovan Peoples-Jones with 11 seconds remaining in the fourth quarter – leading the Browns to a stunning 37–34 comeback victory. Mayfield was named AFC Offensive Player of the Week for his performance in Week 7.
Mayfield was placed on the reserve/COVID-19 list on November 8 after being in close contact with a person who tested positive for the virus, and was activated three days later. In Week 13 against the Titans, Mayfield completed 25 of 33 passes for 334 yards. His four touchdown passes all came in the first half, as the Browns defeated the Titans by a score of 41–35. Mayfield's four first-half TDs tied Otto Graham for a franchise record. Mayfield came close to throwing six first-half TDs, as Peoples-Jones dropped a would-be touchdown, leading to a field goal, and running back Nick Chubb wrapped up the scoring with a one-yard run near the end of the first half after Mayfield completed a 17-yard pass play to Rashard Higgins, setting up Chubb for the score. The Browns scored on all six of their first half possessions. The victory gave the Browns a 9–3 record, clinching the Browns' first winning season since 2007. Mayfield was named the FedEx Air player of the week for Week 13. In Week 14 against the Ravens, Mayfield threw for 343 yards, 2 touchdowns, and 1 interception as well as rushing for 23 yards and a touchdown during the 47–42 loss. In Week 16 against the Jets, Mayfield lost a fumble on fourth down with 1:25 remaining in the game while attempting a quarterback sneak during the 23–16 loss. In Week 17, Mayfield and the Browns defeated the Pittsburgh Steelers 24–22 and earned their first playoff berth since 2002, at which time Mayfield was seven years old. The Browns finished the 2020 regular season 11–5.
In the Wild Card Round against the Pittsburgh Steelers, Mayfield went 21 of 34 for 263 yards and 3 touchdowns during the 48–37 win, leading the Browns to their first playoff victory since the 1994 season, the year before Mayfield was born. It was also the Browns' first playoff road victory in 51 years, way back in 1969. In the Divisional Round of the playoffs against the Kansas City Chiefs, Mayfield threw for 204 yards, 1 touchdown, and 1 interception during the 22–17 loss.
Overall, Mayfield finished the 2020 season with 4,030 passing yards, 30 touchdowns, and nine interceptions through 18 total games. He was ranked 71st by his fellow players on the NFL Top 100 Players of 2021.
The Browns exercised Mayfield's fifth-year contract option for the 2022 season on April 23, 2021, worth $18.9 million guaranteed. On October 7, 2021, it was revealed that Mayfield was playing with a partially torn labrum which he suffered during the Browns' Week 2 victory over the Texans. Mayfield continued to play with the injury until reaggravating it in Week 6 against the Arizona Cardinals. Due to the injury, Mayfield was ruled out for the Browns' Week 7 game against the Denver Broncos, missing his first game since taking over as the Browns' starter in 2018. On November 14, 2021, Mayfield suffered a right knee contusion during their crushing Week 10 loss to the New England Patriots. While the injury was not severe, coach Kevin Stefanski decided not to put him in for the rest of the game due to Mayfield absorbing hits and the game being out of reach. After the Browns were eliminated from the postseason following a Week 17 loss to the Steelers, the Browns announced Mayfield would undergo surgery on the torn labrum, ending Mayfield's season. He was placed on injured reserve on January 5, 2022. Mayfield threw for 3,010 yards, 17 touchdowns, and 13 interceptions in 14 games played.
In the 2022 offseason, after the Browns traded for quarterback Deshaun Watson and signed him to a contract extension, Mayfield requested that the team trade him.
