The son of former NFL quarterback Gale Gilbert, he played college football for the Texas Longhorns and SMU Mustangs.

Joining the NFL in 2014, Gilbert was primarily assigned to his teams' practice squads during his first four seasons and appeared in only one game with the Carolina Panthers.

He came to prominence in 2019 as the starting quarterback for the Orlando Apollos of the Alliance of American Football (AAF), where he led the league in passing yards and passer rating.

Gilbert rejoined the NFL after the AAF suspended operations and started games for the Dallas Cowboys and Washington Football Team.

"[1] Gilbert guided Lake Travis to the 2007 Texas UIL Class 4A Division II State Championship.

[8] An ESPN columnist pointed out that Gilbert was the most likely player from the camp to win the college football national championship.

[12] Gilbert verbally committed to play college football for the Texas Longhorns on February 7, 2008, the day after he received the offer in the mail.

[14] Alongside Matt Barkley of Mater Dei High School in California, Gilbert was the premier quarterback prospect of the class of 2009.

In the 2009 season opener against Louisiana-Monroe, Gilbert lined up behind center during the fourth quarter and drove the Longhorns down the field, completing four-of-five passes for 46 yards, before scoring a twelve-yard rushing touchdown on a quarterback draw play to end the drive.

One analyst took the position that his stat line did not reflect how well he actually played (even though he was responsible for five turnovers – the four interceptions and a lost fumble), and that several of his passes that should have been caught were dropped.

[29] Soon after that year's bowl season, Mack Brown announced that every job was up for grabs, leaving Gilbert to compete with sophomores Case McCoy and Conner Wood, as well as freshman David Ash.

[citation needed] On August 29, it was announced that Gilbert would retain the starting position in the season opener against Rice.

[30] However, on September 12, it was announced that he was being demoted to the second-string quarterback behind Case McCoy and Ash, who would share the starting position.

[34] Gilbert won the starting job at SMU, where he ran June Jones's run and shoot offense.

[49] On January 2, 2017, he was signed to the Raiders' practice squad after Matt McGloin suffered an injury in the final game of the regular season.

[59] On November 27, 2018, Gilbert was selected by the Orlando Apollos in the Alliance of American Football's quarterback draft.

[61] During the inaugural game of the 2019 season against the Atlanta Legends, Gilbert went 15 for 25 for 227 yards, with two passing touchdowns and a receiving score in the 40–6 win.

[63] When the AAF suspended operations after Week 8, Gilbert led the league in passing yards (2,152), attempts (259), completions (157), and passer rating (99.1).

[65] He made his debut with the Browns in Week 5, relieving Baker Mayfield in the fourth quarter of a 3–31 loss to the San Francisco 49ers.

[70] On October 12, 2020, Gilbert was signed by Cowboys off the Browns practice squad as a backup to Andy Dalton after Dak Prescott suffered a season-ending ankle injury.

[73][74] In his first NFL start, he threw for 243 yards, one touchdown, and one interception, nearly pulling off an upset as the Cowboys ultimately lost 24–19.

[84] On October 15, Gilbert was elevated to the active roster to be the backup quarterback to rookie Bailey Zappe as both Mac Jones and Brian Hoyer were both injured.

[88] He was born in Buffalo, New York, where his father played for the Bills in the early 1990s as a member of the teams who lost four consecutive Super Bowls.

He moved to San Diego, California, at age three, when Gale signed with the Chargers, who also played in and lost the Super Bowl.