He and teammate Wes Unseld quickly became a formidable combination in Baltimore, and Monroe became a cult hero for his ability to run the fast break and for his circus-like shots. He said, "The thing is, I don't know what I'm going to do with the ball, and if I don't know, I'm quite sure the guy guarding me doesn't know either." On February 6, 1970, he set an NBA record with 13 points in one overtime in a double-overtime victory over the Detroit Pistons (another mark since surpassed by Arenas).
In 1971, Monroe was traded to the New York Knicks and formed what was known as the "Rolls Royce Backcourt" with the equally flamboyant Walt Frazier. While there were initial questions as to whether Monroe and Frazier could coexist as teammates, the duo eventually meshed to become one of the most effective guard combinations of all time, leading the Knicks to the 1973 NBA championship. That pairing is one of few backcourts ever to feature two Hall of Famers and NBA 50th Anniversary Team members.
A four-time NBA All-Star, Monroe retired after the 1980 season due to serious knee injuries, which had plagued him throughout his career. He had played 926 NBA career games, scored 17,454 total points (18.8 ppg) and dished out 3,594 assists. Monroe had his number 15 jersey retired by the Knicks on March 1, 1986.
Even Monroe admits that his flowing, fluid, silky-smooth on-court style of play was unique. He has said: "You know, I watch the games and even now I never see anyone who reminds me of me, the way I played."
Monroe has also been active in various community affairs and programs, including the President's Council on Physical Fitness and Health, the Crown Heights Youth Collective, the Literary Assistance Fund and the Harlem Junior Tennis Program. He has received many honors for these "off-the-court" community activities, including the Harlem Professionals Inspirational Award, Most Outstanding Model for American Youth, the YMCA Citizenship Award and Big Apple Sportsman of the Year Award.
In October 2005, Monroe opened a restaurant in New York City, named "Earl Monroe's Restaurant & Pearl Club". However, Monroe has since revoked the licensing rights to his name and the restaurant is now called The River Room.