The Chicago Bulls selected Van Lier in the third round of the 1969 NBA draft, but immediately traded him to the Cincinnati Royals, with whom he led the NBA in assists in 1971. 

On January 5 of that year, Van Lier became the first player in NBA history to have a scoreless double-double with zero points, 13 assists and 11 rebounds in a victory against the Los Angeles Lakers.

The Bulls reacquired Van Lier during the 1971–72 season, and he remained with the Bulls until 1978, appearing in three All-Star games (1974, 1976, 1977) over the course of six seasons.

Nicknamed "Stormin' Norman" for his tenacity and aggression, Van Lier was one of the most popular Bulls players of the 1970s. During his ten-year career, Van Lier was named to three NBA All-Defense First Teams and five NBA All-Defense Second Teams. 

He has the most selections alongside Michael Cooper to not be inducted into the Naismith Basketball Hall of Fame. He was named to the All-NBA Second Team in 1974. Van Lier was waived by the Bulls in October 1978.

On January 19, 1977, Van Lier broke the record for the longest successful field goal in NBA history at 84 feet; the record stood for 24 years until Baron Davis eclipsed it on November 17, 2001, from a distance of 89 feet.

After playing briefly with the Milwaukee Bucks, Van Lier retired in 1979 with career totals of 8,770 points and 5,217 assists.