J.B. Brown was a 6' defensive back out of the University of Maryland. Miami selected him in the 12th round of the 1989 NFL Entry Draft, 315th overall.
As a rookie, Brown appeared in all 16 games for Miami, mostly on special teams. Miami finished 8-8 and Brown collected a total of nine tackles.
Brown was Miami's starting right cornerback in all 16 games in 1990. He totalled 48 tackles and one sack as the Dolphins finished 12-4. Miami's defense allowed an NFL fourth lowest 242 points, eventually advancing to the second round of the playoffs.
In 1991, Brown started 11 of the 15 games in which he appeared. He finished with 55 tackles and intercepted his first career pass in a week six 20-10 victory over the New England Patriots. Miami finished with an underwhelming 8-8 record, missing out on the postseason dance.
1992 would see Brown start all 16 games for Miami. He would score the first touchdown of his career on a 35 yard interception return in a week 14 20-7 victory over the Oakland Raiders. He intercepted a total of four passes for 119 return yards along with a fumble recovery and 56 tackles. The Dolphins finished up 11-5, eventually falling in the AFC Championship game.
In 1993, Miami finished up 9-7 as Brown made 72 tackles along with a career high five interceptions. 1994 would see him collect a career high and team third best 76 tackles along with three picks. The team went 10-6, advancing to the second round of the playoffs.
Brown would start 12 of 13 games for Miami in 1995, intercepting two passes for 20 yards in a week three victory over the Pittsburgh Steelers, 23-10. He also finished with 47 tackles, two forced fumbles and two fumble recoveries.
Brown totalled 122 games for Miami, starting 88 at the right cornerback position. He intercepted 16 passes with 377 tackles while with the franchise.