Longley was drafted 7th overall by the Minnesota Timberwolves in 1991. After two plus mediocre seasons with the struggling franchise, the 7'2" (218 cm) center was dealt to the Chicago Bulls for Stacey King late in the 1993-94 season.

In 1995 Michael Jordan returned to the Bulls after a nearly two year retirement and helped the team win three consecutive NBA titles. Longley meanwhile, acted as starting center in each of the championship seasons.

Following the break up of the championship Bulls in 1999, Chicago did a sign and trade with Longley, sending him to the Phoenix Suns for Mark Bryant, Martin Muursepp, Bubba Wells and a conditional first-round draft pick. Longley spent two lackluster seasons with Phoenix until he was traded to the New York Knicks prior to the 2000-2001 NBA season in what was then only the second four-team trade in NBA history. The Suns acquired Chris Dudley as part of the deal together with a first-round draft pick from New York and an undisclosed amount of cash, while New York received Longley, Glen Rice, Travis Knight, Vladimir Stepania, Lazaro Borrell, Vernon Maxwell, two first-round draft picks (from the Los Angeles Lakers and the Seattle SuperSonics) and two second-round draft picks from Seattle. Seattle received Patrick Ewing and the Lakers received Horace Grant, Greg Foster, Chuck Person and Emanual Davis. Longley spent one year with New York before retiring. Longley averaged 7.2 points and 4.9 rebounds per game in his 567 regular season game NBA career.

Some in Australia feel Longley did not appear in enough international matches with the Australian Boomers during his career. That however, may be due to the various knee injuries that eventually ended his playing days.

Longley attended Scotch College, Perth for the majority of his high schooling, was part owner of the Perth Wildcats basketball club in the Australian National Basketball League for several years, and is currently the #1 ticket holder of the Fremantle Football Club in the Australian Football League.