Smith was born on May 6, 1993 in Tallahassee, Florida . He is one of four children to Michael and Loretta Smith. He attended James S. Rickards High School , where he played both baseball and American football; he played safety in the latter sport.
Smith was drafted by the Milwaukee Brewers in the 13th round of the 2011 Major League Baseball Draft out of high school. He did not sign with the Brewers and instead played college baseball at Santa Fe College . In his only collegiate baseball season, Smith hit for a .380 batting average, 17 extra-base hits, 17 runs batted in, and stole 31 bases. He was then drafted by the San Diego Padres in the fifth round of the 2012 Draft . He signed with the Padres for a $375,000 signing bonus and made his professional debut that season with the Arizona League Padres . He also played for the Eugene Emeralds that year, hitting .305 with two home runs and 17 stolen bases between the two teams.
Smith opened the 2013 season with the Fort Wayne TinCaps . He played in 110 games, hitting .262/.367/.340 with four home runs and 64 stolen bases; the stolen bases were one short of the TinCaps record. Smith started 2014 back with Fort Wayne. During the season he was promoted to the Lake Elsinore Storm . He finished the year hitting .310 with five home runs and led all minor league players in stolen bases with 88.
Atlanta Braves (2016)
On December 19, 2014, the Padres traded Smith, Dustin Peterson , Max Fried , and Jace Peterson to the Atlanta Braves in exchange for Justin Upton and Aaron Northcraft . Smith was invited to attend spring training with the Braves, despite not having any Double A experience at the time. He began the 2015 season with the Mississippi Braves , appearing in 57 games, hitting for a .340 batting average and a .418 on-base percentage, before being promoted to the Gwinnett Braves of the Class AAA International League in June. Smith finished the season at Class AAA, hitting .306, with a .706 on-base plus slugging percentage for the year. He was named the Braves' Minor League Player of the Year for all levels and added to the 40-man roster after the season.
Smith started the 2016 season with Gwinnett. The Braves promoted Smith to the Major Leagues on April 11, 2016. He debuted that night against the Washington Nationals , starting in center field. Smith went 1-for-3 with a strikeout and a single against Max Scherzer . Smith's helmet lacerated his forehead on a stolen base attempt in the 4th inning, and he left the game.  Two days later, Smith recorded his first stolen base against the same team. 
On April 17, he collected his first career RBI and helped the Braves sweep the Miami Marlins .
On June 20, Smith fractured his thumb after Mets pitcher Antonio Bastardo hit him with a fastball. The next day, Smith was placed on the disabled list and expected to miss eight to ten weeks of the season. After a July reevaluation, his return date was moved to September. Braves interim manager Brian Snitker later stated that Smith would likely miss the remainder of the season.
On January 11, 2017, the Braves traded Smith, along with Shae Simmons , to the Seattle Mariners in exchange for Minor League pitchers Luiz Gohara and Thomas Burrows.  Later that day, the Mariners agreed to trade Smith, Ryan Yarbrough, and Carlos Vargas to the Tampa Bay Rays for Drew Smyly . 
Tampa Bay Rays (2017-Present)
Mallex Smith was on the Opening Day starting lineup for the first time in his career. He wore the #0, a first in the Rays' franchise history. [✔]