Brunson, whose given first name is Eric, played four seasons at Temple in Philadelphia, leading the team to the NCAA tournament each season. He averaged 12 points and 3.8 assists per game during his college career.

After college, Brunson was not selected in the 1995 NBA draft. He was waived twice by the Orlando Magic and the Knicks before signing as a free agent with the Portland Trail Blazers in 1997. He joined the New York Knicks in 1999 and was on the roster of the team that reached the NBA Finals. Brunson also played for the Boston Celtics, Chicago Bulls, Toronto Raptors, Los Angeles Clippers, Seattle Supersonics, and Houston Rockets.

Brunson ended his playing career in 2006 and was hired as an assistant coach with the Denver Nuggets in 2007. He has coached on staffs as an assistant with the Chicago Bulls, Charlotte Bobcats, and Minnesota Timberwolves, and has been an assistant with the Knicks since 2022, the same year his son, Jalen, signed a four-year, $104 million free-agent contract with New York.

In 2018, Brunson resigned from the Timberwolves amid allegations of improper conduct toward women, with the team saying that they were "committed to creating a safe work environment for our employees, partners and fans and expect our staff to lead by example," and "did not believe Mr. Brunson’s conduct was consistent with those standards.”

In 2014, he was acquitted of attempted criminal sexual assault, criminal sexual abuse, aggravated battery, and domestic battery after a massage therapist, with whom he admitted to being in an extramarital relationship, accused him of grabbing her arm and trying to perform a sex act.