Robinson was selected by the Milwaukee Bucks with the first overall pick in the 1994 NBA draft, the first Boilermaker to be selected as the first pick since Joe Barry Carroll in 1980. Before he could take the court, he and the Bucks became involved in a contract holdout that lasted until the beginning of training camp after it was rumored that he desired a 13-year, $100 million contract. Robinson eventually signed a rookie-record 10-year, $68 million deal that still stands as the richest NBA rookie contract, as a salary cap for rookies was implemented the following season. During his first year in the NBA, Robinson was twice named the Schick NBA Rookie of the Month and was named to the NBA All-Rookie First Team after leading all rookies with an average of 21.9 points per game. Robinson finished third in Rookie of the Year voting behind Grant Hill and Jason Kidd, who shared the award, but was named Rookie Of The Year by Basketball Digest magazine. While playing for the Milwaukee Bucks, Robinson recorded some of the best statistical seasons in franchise history. Early in his career, Robinson shared the frontcourt with teammate and All-Star Vin Baker. After Baker departed, he teamed with Ray Allen and Sam Cassell, and helped lead the Bucks to the 2001 Eastern Conference Finals, losing to the Philadelphia 76ers. Robinson is the second place all-time leading scorer in Milwaukee Bucks history, only trailing Kareem Abdul-Jabbar, averaging at least 20 points per game in seven of his eight seasons in Milwaukee. He made back-to-back NBA All-Star Team appearances in 2000 and 2001.

Robinson was traded by Milwaukee to the Atlanta Hawks for Toni Kukoč, Leon Smith, and a 2003 first-round pick on August 2, 2002. In Robinson’s debut as a Hawk in the season opener, he scored 34 points, had 10 rebounds and 8 assists against the New Jersey Nets. During the 2002–03 season, he averaged 20.8 points a game and shot a personal-best 87.6 percent from the free throw line.

After a year in Atlanta, he was traded on July 23, 2003 with a 2006 second-round pick to the Philadelphia 76ers in a four-team deal. In his tenth overall and only season playing with the Sixers, Robinson averaged 16.6 points and 1 steal per game as second scoring option to teammate, Allen Iverson. After his year in Philadelphia during the 2003–04 season, Robinson did not play a game for the 76ers in 2004–05, largely due to an injury. On February 24, 2005, he was traded to the New Orleans Hornets in exchange for forwards Rodney Rogers and Jamal Mashburn. Robinson was waived by the team almost immediately and never suited up for them.

Robinson signed with the San Antonio Spurs on April 4, 2005 to establish an additional veteran shooting presence as the team prepared for the playoffs. As a role player in the 2005 playoffs, Robinson helped the Spurs win the championship. The games in the NBA Finals would be Robinson’s last in the NBA, capping off his 11-year career with a title.

Robinson left Purdue after becoming the only Boilermaker to have more than 1,000 points, 500 rebounds, 100 steals, 100 assists and 50 blocked shots in a career during his two seasons at Purdue, along with a school weightlifting record with a 309-pound clean-and-jerk. His 1,030 points during his junior year made him only the 15th player in college history to score 1,000 points in a season. In September 2010, the Big Ten Network named Robinson Icon No. 35 on its list of the biggest icons in Big Ten Conference history.

His younger son, Gelen (class of 2014), is the 2013 Indiana High School Athletic Association (IHSAA) 220-pound (100 kg) wrestling champion, the 2013 IHSAA shot put runner-up, the 2013 IHSAA discus runner-up, and a repeat (2012 and 2013) winner of The Times of Northwest Indiana Football Defensive Player of the Year and as a result the 2012–13 Times of Northwest Indiana Athlete of the Year. Gelen played for the Purdue University football team and signed with the CFL BC Lions in 2018.