Williams, 6 ft 8 in (2.03 m), ranks 13th all-time in NBA career rebounds. His 17-year NBA career was highlighted by three All-Star Game appearances, a Rookie of the Year award, an All-Rookie team selection, an All-NBA second team selection and four selections to the first and second NBA All-Defensive teams. As of 2010, he is still the Nets' all-time leader in points (10,440), total rebounds (7,576), rebounds per game (11.9), and free throws made (2,476).
Williams attended Rocky Mount High School (then called Rocky Mount Senior High) in Rocky Mount before going off to play collegiately at the University of Maryland. Williams had immediate success at Maryland, capturing the ACC Rookie of the Year Award in 1979. He led the ACC in rebounding twice (1979 and 1981), while averaging 15.5 points per game in his sophomore and junior years. He earned All-ACC honors in 1980 and 1981. National recognition of his performances came when he was selected to the 1980 USA Olympic basketball team, alongside such players as later two-time NBA champions Isiah Thomas and Mark Aguirre; he, however, never got to represent the national colors in Moscow due to the United States' boycott. In 2002, Williams was one of eight former Maryland players to be named to the ACC 50th Anniversary men's basketball team. In 2001, he became a member of the University of Maryland’s Athletic Hall of Fame.
After three years at Maryland, Williams decided to leave for the NBA. The New Jersey Nets selected him third overall in the 1981 NBA Draft, behind Olympic teammates Aguirre and Thomas. In his first season with the Nets, he averaged 15.5 points and led the team with 12.3 rebounds per game, helping New Jersey win 20 more games (a 44-38 win-loss record) than the previous year and earning 1982 Rookie of the Year honors. Williams established himself as a premier player at the power forward position over the next eight seasons with the Nets; in six of those he was ranked among the best three rebounders in the league, never averaging less than twelve rebounds per game. This period (1984) featured the Nets' best playoff effort since the ABA-NBA merger in 1976 - their first second-round appearance, where they lost to the Milwaukee Bucks; not until 2002 did the Nets get past the first round of the playoffs again.
On June 24, 1989, the Nets traded Williams to the Portland Trail Blazers in exchange for Sam Bowie and a draft pick. In Portland, Williams would continue his solid play and take a complementary frontcourt role to established guard duo of Clyde Drexler and Terry Porter. The Blazers' post-season campaigns ended in the first round four consecutive years prior to 1990; contrastingly, Wiliams' first three seasons with the Blazers were marked by three Western Conference Finals appearances and two NBA Finals. In 1990 the Blazers succumbed to the powerhouse Detroit Pistons in five games, while in 1992 they fell to the Chicago Bulls in six. Williams was regularly in the starting lineup for the first six of his seven seasons with the Blazers. He remains the franchise leader in field goal percentage (55.0%).
In the twilight of his career, after the 1995-96 season, Williams moved back to the Atlantic Division, signing with the New York Knicks, where he played in a much more limited capacity, behind the frontcourt duo of Patrick Ewing and Charles Oakley. He spent two years with the Knicks, but was forced to miss 41 games during 1997-98 season due to knee surgery (the first time in his career he missed more than 12 games in a season). Williams announced his retirement on January 27, 1999, holding career averages of 12.8 points and ten rebounds per game and a field goal average of 54.9 percent. During the course of his 17 year NBA career, Williams racked up more than 16,000 points and 13,000 rebounds — one of only seven NBA players to ever reach both marks.
Williams served as the president of the NBA Players Association from 1994 to 1997. The Nets retired his #52 jersey in April 1999. In 2006 he was named as an inductee into the Rocky Mount Twin County Hall of Fame.
Currently, Buck Williams has a construction company and is involved in several charities including Global Giving where he competes with other athletes around the country to raise money for local causes.