He played college football for the SMU Mustangs and Sam Houston Bearkats, and was selected by the Arizona Cardinals in the third round of the 2002 NFL draft.

In his only season with the Bearkats, he threw for 3,481 yards, 32 touchdowns and 12 interceptions, earning Southland Football League Player of the Year and Third-team Division I-AA All-American honors.

[7] McCown played college football for the SMU Mustangs of Southern Methodist University from 1998 to 2000, passing for 4,022 yards and 27 touchdowns, but also threw 34 interceptions.

[40][41] McCown made his NFL debut on December 1 against the Kansas City Chiefs, relieving starter Jake Plummer late in the third quarter of an eventual 49–0 loss.

On September 14 against the Seattle Seahawks, McCown completed 18 of 32 passes for 150 yards with 2 interceptions after relieving the injured Blake late in the first quarter of an eventual 38–0 loss.

[46][50][51] Head coach Dave McGinnis stated, "Josh is the right decision professionally for our organization," and "Some quality time is what he needs against good teams ... and it's important to find out what we have there.

[56] During McCown's ninth consecutive start on November 14 against the New York Giants, he completed 12 of 24 passes for only 90 yards, though the Cardinals won the game by a score of 17–14.

[67] McCown's next start was against the Carolina Panthers on October 9, in which he completed 29 of 36 passes for a new career-high of 398 yards with 2 touchdowns and 3 interceptions as the Cardinals lost by a score of 24–20.

[72][73][74] In Warner's seventh start back against the Houston Texans on December 18, he suffered an injury early in the first quarter and stayed in the game for two more series before being relieved by McCown.

Later the same day, McCown and wide receiver Mike Williams were traded to the Oakland Raiders in exchange for a 2007 fourth-round draft pick, which the Lions used to select cornerback A. J.

[89] However, he did not publicly name the starter until the day of the Week 1 game against the Lions on September 9, explaining, "It's simply a matter of always trying to gain a competitive advantage.

[158][159] On December 21, 2011, the Bears announced that McCown would start on the Christmas Day game against the defending champion Packers, due to Hanie's struggles since taking over for the injured Cutler.

[170] On November 4, McCown, starting in place of the injured Cutler, led the Bears to a victory over the rival Packers on Monday Night Football.

[178][179] McCown ended the 2013 season completing 66.5 percent of his passes for 1,829 yards with 13 touchdowns, 1 interception, and a 109.0 passer rating, the third-highest behind Peyton Manning and Nick Foles and the best in Bears history.

[202][203][204] McCown returned from his injury in a Week 3 game against the Raiders on September 27, where he threw for 341 yards, 2 touchdowns, and 1 interception as the Browns lost by a score of 27–20.

[209][182] The jerseys that McCown and teammate Gary Barnidge wore during the Week 5 Ravens game were sent to, and displayed, at the Pro Football Hall of Fame.

[223] In the ensuing Week 12 rematch against the Ravens on December 1, McCown broke his collarbone late in the third quarter and stayed in for two plays before leaving the game.

[230] The local chapter of the Pro Football Writers of America named McCown its Dino Lucarelli Good Guy Award winner.

[243][244] On November 10 against the Ravens, McCown threw for 59 yards with no touchdowns and 2 interceptions after entering the game early in the third quarter due to Kessler being benched.

[262] During Week 14 against the Broncos, McCown threw for 46 yards while also turning the ball over twice on an interception and a fumble before leaving the game late in the third quarter after an apparent hand injury as the Jets lost by a score of 23–0.

[264] The next day, head coach Todd Bowles announced that McCown would undergo surgery on his left hand, putting him out for the remainder of the 2017 season.

[269] Eventually, Darnold was named the team's starter after Bridgewater was traded to the Saints, solidifying McCown's role as the primary backup going into the 2018 season.

[270] With Darnold inactive due to a right foot injury, McCown started in Week 10 against the Buffalo Bills, where he finished with 135 passing yards and two interceptions as the Jets lost 41–10.

[280] McCown mentored Wentz, and several wide receivers on the practice squad, as the Eagles won four straight games to win the division title and reach the playoffs after a 5–7 start marred by numerous injuries.

[281][282][283][284] In the Wild Card Round of the 2019–20 NFL playoffs, McCown entered the game in the first quarter in relief of an injured Wentz, who suffered a helmet-to-helmet collision with the Seahawks' Jadeveon Clowney.

[291] Following the playoff loss, the Eagles offered McCown a role on the team's coaching staff for the 2020 season, but he declined, as he was still interested in continuing his playing career.

[39] McCown previously spent time as a volunteer quarterbacks coach for the Marvin Ridge High School Mavericks of Waxhaw, North Carolina.

"[3] McCown also cooked pancakes for the Fellowship of Christian Athletes breakfasts on Fridays and spent time teaching physical education classes at Marvin Ridge.

[3][304][305] McCown also served as an assistant coach at Myers Park High School in Charlotte, North Carolina, where his sons Owen and Aiden played.

[322][321][303][39] He was also a fan of Cowboys players Michael Irvin, Emmitt Smith, and Troy Aikman, as well as quarterbacks Joe Montana, John Elway, and Randall Cunningham.