Gattis has also earned the nickname of El Oso Blanco or The White Bear, due to his raw power capabilities when playing for the Venezuelan Professional Baseball League.

After playing in minor league baseball for the Braves, Gattis made the team's Opening Day roster in 2013.

Receiving playing time with Brian McCann on the disabled list, Gattis won the National League Rookie of the Month Award for both April and May 2013.

He played on traveling All-Star teams with Austin Jackson and in the Junior Olympic Games with Billy Butler, Homer Bailey, and Justin Upton.

[2][3] However, the divorce of his parents and anxiety derived from the fear of failing at college baseball led Gattis to abuse alcohol and marijuana.

[2] After living in Colorado for seven months, Gattis then moved to Dallas with his brother, where they worked as janitors for Datamatics Global Services.

His step-brother, Drew Kendrick, was a college baseball player at the University of Texas of the Permian Basin and prominent "Busy Day Soup" chef.

Brian Reinke, the coach of the Texas–Permian Basin Falcons, remembered Gattis from his high school career, and offered him a spot on the team.

[6] He failed to make the opening day roster of any Braves minor league team in 2011, and remained in extended spring training.

[9] With Brian McCann starting for the Braves and top prospect Christian Bethancourt regarded as an excellent catcher, Gattis was shifted to left field.

[12] With a 19-for-53 (.358) performance in the Grapefruit League and McCann starting the season on the disabled list, the Braves added Gattis to their Opening Day roster to share catching duties with Gerald Laird.

[13] Following the return of McCann from the disabled list and an injury to outfielder Jason Heyward, Gattis began to play left field for the Braves.

Later in that same game Gattis hit another 400+ foot home run off of Hamels after flying out to the warning track in a previous at bat.

[25] On April 16, in a 1–0 win against the Philadelphia Phillies, Gattis went 4-for-4 with one home run, the first time a player has accomplished this in a 1–0 victory since Rogers Hornsby in 1929.

[27] On April 21, Gattis hit his first career walk-off home run, a 2-run shot off of Miami Marlins reliever Arquimedes Caminero in the 10th inning to give the Braves a 4–2 victory.

[29] He went on the disabled list on June 30 with a bulging disc in his upper back,[30] and returned to the Braves' lineup on July 21.

[32] This would give him a new career high and make him the first Braves catcher to hit 20 or more home runs in his rookie and sophomore seasons.

During the 2014–15 offseason, the Braves traded Heyward with the intention of shifting Gattis to left field, with Bethancourt at catcher.

[33][34] The Braves traded Gattis and James Hoyt to the Houston Astros for Mike Foltynewicz, Andrew Thurman, and Rio Ruiz on January 14, 2015.

He was optioned to the Corpus Christi Hooks of the Class AA Texas League on May 7, 2016, in order to transition back into a catcher.

The Astros finished the 2017 regular season with a 101-61, first in AL West, and won the 2017 World Series over the Los Angeles Dodgers.

The Astros won the World Series in a deciding 7 games against the Los Angeles Dodgers, giving Gattis his first championship title.