Dejean-Jones attended View Park Preparatory High School for two years, then transferred to and graduated from William Howard Taft Charter High School in the Woodland Hills section of Los Angeles. As a senior in 2009–10, he averaged 16.9 points, 7.5 rebounds, 1.9 assists, 1.6 steals and made 56.8 percent of his shots, including 49.3 percent from beyond the arc in leading the Toreadors to the L.A. City Section final and third round of the Division I state playoffs.
Dejean-Jones began his college career with USC, appearing in 18 of 34 games as a freshman and starting in each of the Trojans' first 10 games. In 20.6 minutes per game, he averaged 7.6 points, 2.6 rebounds, 1.6 assists and 1.1 steals per game while shooting 37.9 percent from the field and 34.5 percent from three-point range, scoring in double figures seven times, including a career-high 21 points against New Mexico State.
After his freshman season, Dejean-Jones transferred to UNLV, redshirting as a sophomore. As a redshirted sophomore in 2012–13, he was named the Mountain West Preseason Co-Newcomer of the Year prior to the start of the season, going on to appear in all 35 games, starting 29. He was third in scoring for the Runnin' Rebels with 10.3 points per game, third in steals and assists with 0.9 and 2.3 per game respectively, and fourth in rebounds with 4.4 rebounds per game, leading his the team in scoring five times and in rebounding twice. He made his debut on November 12, 2012, scoring 15 points, including hitting 3-of-4 three-pointers, in a win over Northern Arizona which was the first of 18 total games of scoring in double figures. He also dished out a career-high six assists in three different games, and exploded for a career-high 22 points on 7-of-11 shooting in a 76–75 win over California to help UNLV earn its best non-conference road win of the season. On February 9, 2014, he grabbed a career-high nine rebounds in a home win over New Mexico and made a career-high five three-pointers as part of a team-leading 19-point effort in the MW Tournament's Championship game on March 16, also against the Lobos. Five days later, he made his NCAA Tournament debut against Cal, scoring a team-high 15 points in a 64–61 loss.
In 2014, Dejean-Jones transferred to Iowa State to play under coach Fred Hoiberg. Dejean-Jones played in 33 games during the 2014–15 season, starting 21, averaging 10.5 points, 4.7 rebounds, 2.1 assists and 1.1 steals, while shooting a career-best 47.6 percent from the field. He scored in double figures 17 times and earned CBSSports.com National Player of the Week honors after scoring a season-high 27 points in ISU's win against nationally-ranked Arkansas. In that game, he was 8-for-8 from the field, becoming just the fifth player in school history with at least eight field goal attempts in a game without a miss. In his Cyclone debut, he recorded his first career double-double, finishing with 20 points and 11 rebounds against Oakland, and just missed a triple-double against Lamar, scoring 12 points to go along with 10 rebounds and a career-high eight assists. With this efforts, he helped the Cyclones win the 2015 Big 12 Tournament.
After going undrafted in the 2015 NBA draft, Dejean-Jones joined the New Orleans Pelicans for the 2015 NBA Summer League in Las Vegas, averaging 12.8 points in six games. On August 20, 2015, he signed with the Pelicans, but was later waived by the team on October 24 after appearing in seven preseason games. On December 13, he was acquired by the Idaho Stampede of the NBA Development League. He made his professional debut on December 19 in a 117–107 win over the Santa Cruz Warriors, recording 15 points, three rebounds, four assists and one steal in 21 minutes of action.
On January 21, 2016, Dejean-Jones signed a 10-day contract with the Pelicans. On January 28, in his fourth game for the team, Dejean-Jones started at shooting guard in place of the injured Tyreke Evans. In 34 minutes of action, he recorded 14 points, 2 rebounds, 2 assists, 2 steals and 1 block, helping the Pelicans defeat the Sacramento Kings 114–105. On February 1, he signed a second 10-day contract, and continued to start for the Pelicans due to Evans' injury. On February 4, he had a career-best game with 17 points and 9 rebounds in a 99–96 loss to the Los Angeles Lakers. On February 19, he signed a three-year deal with the Pelicans. A week later, he was ruled out for the rest of the season after undergoing successful surgery to repair a right wrist fracture.
Dejean-Jones was the son of Walter Dejean and KC Franchesca Jones, and had four brothers and two sisters. He graduated from UNLV with a degree in sociology and pursued a master's degree in family and consumer sciences – youth development. He had one daughter.
On May 28, 2016, Dejean-Jones died when he was shot after kicking open the locked front door and locked bedroom door of a Knox Park, Dallas apartment he mistakenly thought belonged to his former girlfriend. He was visiting his former girlfriend, who lived on the floor above, for their daughter's first birthday. Dejean-Jones intended to re-enter her apartment after leaving to take a walk following an argument with her, but instead went to another apartment one floor below his former girlfriend's apartment on the 4th floor. At about 3:20 a.m., Dejean-Jones forced open the front door of the third-floor apartment. While shouting for his ex-girlfriend, Dejean-Jones approached and kicked the bedroom door within the apartment. The resident, who had been sleeping, retrieved and fired a handgun at Dejean-Jones through the bedroom door, striking him in the abdomen. Dejean-Jones, 23, was pronounced dead at a Dallas hospital. According to his agent, this was the first time that Dejean-Jones visited his ex-girlfriend's new apartment. Dejean-Jones is the first active NBA player to die since 2007 when Eddie Griffin was killed in a vehicular accident.