Named one of the 50 Greatest Players in history by the NBA in 1996, Barry is the only player to lead the National Collegiate Athletic Association (NCAA), ABA and NBA in scoring for an individual season. In 1987, Barry was inducted into the Naismith Memorial Basketball Hall of Fame.

Barry also ranks on the short list of greatest underdog players in basketball history, as his teams repeatedly overachieved despite marginal talent around him. Longtime NBA writer Paul Ladewski has referred to him as Ricky Balboa, a reference to Rocky Balboa, the prize fighter of motion picture fame who was at his best in the face of long odds.

Barry grew up in Roselle Park, New Jersey and was an All-American basketball player for the University of Miami, where he starred for three seasons. While at Miami, Barry met his wife Pamela, the daughter of Hurricanes head coach Bruce Hale. As a senior in the 1964-65 campaign, Barry led the NCAA with a 37.4 points-per-game average. Barry and the Hurricanes did not take part in the NCAA Tournament, however, because the basketball program was on probation at the time. Barry is one of just three basketball players (along with Tim James and Jack McClinton) to have his number retired by the school.

Barry was drafted by the San Francisco Warriors with the second pick of the 1965 NBA Draft.

In Barry's first season in the NBA with the Warriors, the team improved from 17 to 35 victories. In the All-Star Game one season later, Barry erupted for 38 points as the West team stunned the East squad, which featured Wilt Chamberlain, Oscar Robertson, Bill Russell and head coach Red Auerbach among other all-time greats. Later that season, Barry and company extended the mighty Philadelphia 76ers to six highly competitive games in the NBA Finals, something that Russell and the Boston Celtics could not do in the Eastern Conference playoffs. That 76ers team is considered to be one of the greatest in basketball history.

Nicknamed the "Miami Greyhound" by longtime San Francisco-area broadcaster Bill King because of his slender physical build and remarkable quickness and instincts, the 6'7" Barry won the NBA Rookie of the Year Award after averaging 25.7 points and 10.6 rebounds per game in the 1965-66 season. The following year, he won the 1967 NBA All-Star Game MVP award with a 38-point outburst and led the NBA in scoring with a 35.6 point per game average — which still ranks as the eighth- highest output in league annals. Teamed with star center Nate Thurmond in San Francisco, Barry helped take the Warriors to the 1967 NBA Finals, which they lost to the Philadelphia 76ers in six games. Including a 55-point outburst in Game 3, Barry averaged 40.8 points per game in the series, an NBA Finals record that stood for three decades.

Upset that he was not paid incentive monies that he believed due from Warriors owner Franklin Mieuli, Barry jumped to the ABA's Oakland Oaks, who offered him a lucrative contract and the chance to play for Bruce Hale, then his father-in-law. The three-year contract offer from Pat Boone, the singer and team owner, was estimated to be worth $500,000, with Barry saying "the offer Oakland made me was one I simply couldn't turn down" and that it would make him one of basketball's highest-paid players. The courts ordered Barry to sit out the 1967-68 campaign before he starred in the ABA, upholding the validity of the reserve clause in his contract. The ensuing negative publicity cast Barry in a negative light, portraying him as selfish and money-hungry. However, many NBA players at the time were looking at jumping to the ABA for more lucrative contracts. Barry would star in the ABA, twice averaging more than 30 points per game.

After the 1966-67 season, Barry became one of the first NBA players to jump to the American Basketball Association when he signed with the Oakland Oaks. In the ABA's first season, the Oaks were the only ABA team located in the same market as an NBA team (the Warriors). The Warriors went to court and prevented Barry from playing for the Oaks during the 1967-68 season. Barry instead worked on Oaks radio broadcasts during the ABA's first season.

During the 1968-69 season Barry suited up for the Oaks and averaged 34 points per game. He also led the ABA in free throw percentage for the season (a feat he repeated in the 1970-71 and 1971-72 seasons). However, on December 27, 1968, late in a game against the New York Nets, Barry and Kenny Wilburn collided and Barry tore ligaments in his knee. He tried to play again in January but only aggravated the injury and sat out the rest of the season, only appearing in 35 games as a result. Despite the injury Barry was named to the ABA All-Star team. The Oaks finished with a record of 60-18, winning the Western Division by 14 games over the second place New Orleans Buccaneers. In the 1969 ABA Playoffs the Oaks defeated the Denver Rockets in a seven game series and then defeated New Orleans in the Western Division finals. In the finals the Oaks defeated the Indiana Pacers 4 games to 1 to win the 1969 ABA Championship.

The Oaks' on-court success had not translated into solid attendance. The team averaged 2,800 fans per game. Instead of remaining in Oakland for another season to see if the championship would draw fans, the team was sold by owner Pat Boone and relocated to Washington, DC for the 1969-1970 season.