Smith attended Edison High School in Fresno, California from 2005 to 2008. As a junior in 2007–08, he averaged 22 points, 15 rebounds, five assists and five blocks per game. In 2008, he transferred to Westwind Preparatory Academy in Phoenix, Arizona where as a senior in 2008–09, he earned All-Arizona State honors and was nominated for the McDonald’s All-America Team after he averaged 26 points, 14.4 rebounds, six blocks, four assists and three steals per game.
In his freshman season at Fresno State, Smith was named the 2009–10 WAC Freshman of the Year and earned Freshman All-American honors by CollegeInsider.com. In 33 games (all starts), he averaged 11.5 points, 5.8 rebounds, 1.2 assists and 1.2 blocks in 27.7 minutes per game.
In his sophomore season, Smith earned second-team All-WAC honors. In 31 games, he averaged 11.7 points, 8.1 rebounds, 1.7 assists, 1.1 steals and 1.1 blocks in 30.4 minutes per game.
In March 2011, Smith declared for the NBA draft, forgoing his final two years of college eligibility.
After going undrafted in the 2011 NBA draft, and with the NBA lockout affecting players from signing with teams or playing in the summer league, Smith joined Soles de Mexicali of the Liga Nacional de Baloncesto Profesional (LNBP) in August 2011. He appeared in 27 games for Soles before leaving the club in late November to return to the United States in the wake of the NBA lockout concluding.
On December 13, 2011, Smith signed with the Houston Rockets. However, he was later waived by the Rockets on December 22, 2011 after appearing in two preseason games. On December 28, he was acquired by the Rio Grande Valley Vipers as an affiliate player.
On February 8, 2012, Smith re-signed with the Rockets to a multi-year deal. The next day, he was assigned back down to the Vipers. He was later recalled by the Rockets on February 18, reassigned on March 21 and recalled again on April 8 following the conclusion of the Vipers' season. Having played mostly for the Vipers in his rookie season, Smith was named to the All-NBA D-League first team and the All-Rookie first team.
In July 2012, Smith joined the Rockets for the 2012 NBA Summer League. On February 10, 2013, he was reassigned to the Vipers. Four days later, he was recalled by the Rockets. On March 30, 2013, Smith received his first career start. In 30 minutes of action, he recorded 9 points and 8 rebounds in a 98–81 win over the Los Angeles Clippers. He subsequently remained in the starting lineup for the remainder of the regular season. He went on to start the first game of the Rockets' first round playoff match-up against the Oklahoma City Thunder, but moved back to a bench role for game two following a large Game 1 loss.
In July 2013, Smith re-joined the Rockets for the 2013 NBA Summer League. On November 14, 2013, he injured his right knee during a game against the New York Knicks which resulted in Smith being helped from the floor and missing a month of action. On December 15, he returned to the line-up. However, he re-injured his knee a month later and was sidelined indefinitely. On April 10, 2014, he was waived by the Rockets.
On April 14, 2014, Smith signed with the Chicago Bulls for the rest of the 2013–14 season. However, still suffering from the knee injury he sustained in January, Smith did not appear in a game for the Bulls in 2013–14, missing the team's final two regular season games and all five playoff games against the Washington Wizards.
On July 14, 2014, Smith was traded to the Dallas Mavericks in exchange for the rights to Tadija Dragićević. He became a free agent in the summer of 2015.
On January 5, 2016, Smith was acquired by Raptors 905 of the NBA Development League. He made his debut for the team two days later, recording 15 points, 3 rebounds, 6 assists, 1 steal and 1 block as a starter in a 102–98 loss to the Sioux Falls Skyforce.
On March 2, 2016, Smith signed a 10-day contract with the Minnesota Timberwolves. He made his debut for the Timberwolves later that night in a 104–98 loss to the Washington Wizards, recording four points, one rebound and one assist in 10 minutes off the bench. He later signed a second 10-day contract with the Timberwolves on March 12, and a rest-of-season contract on March 23. On June 30, 2016, he was waived by the Timberwolves.
On October 7, 2016, Smith signed with İstanbul BŞB of the Turkish League. He appeared in seven games for İstanbul before parting ways with the team in late November.
On March 4, 2017, Smith signed with Blackwater Elite as an import for the 2017 PBA Commissioner's Cup. In 10 games, he averaged 27.7 points, 21.2 rebounds, 5.1 assists, 1.2 steals and 1.0 blocks per game.
On August 8, 2017, Smith signed with Osaka Evessa of the Japanese B.League.
Smith is the son of Cheryl Duckworth and has an older sister, Ashely and a younger brother, Divante. His uncle, Steve Shelley, was a Fresno Statewide-receiver in 1988–89 who later signed with the San Diego Chargers in 1990.