Drafted in the 7^th round by Hank Stram and the Kansas City Chiefs in 1963, Bell was listed as a defensive lineman on the KC roster for two years. Often he would use his exceptional athletic skills, as a deep snapper on punts and kicks and as a defensive tackle would drop back into the line backing position. Coach Stram once said, "Bobby Bell was the most versatile athlete I ever coached."

Although considered by Stram to be "big enough, strong enough and fast enough to play any of the 22 positions in football, Kansas City chose to use Bell's talents on the defensive side of the ball. He was a fast learner and earned all-league honors in just his second year. Beginning as a defensive end, Bobby Bell was a ferocious tackler and feared pass rusher. He scored 8 touchdowns and had 25 interceptions.

Bell played his entire NFL career as a member of the Kansas City Chiefs and was the first Chief to be elected to the NFL Hall of Fame. Bobby played in the last 6 AFL All Star games, first 3 AFC-NFC Pro Bowls and was named All AFC and/or All NFC nine times. Teamed with fellow HOF member, Willie Lanier, Bell helped lead the Chiefs to AFL Championships in 1966 and 1969 and to a 23-7 victory over the Minnesota Vikings in Super Bowl IV.