Born in Portland, Maine to attorney Leonard Nelson and his wife, Merle Nelson, (attorney and state assemblywoman), Judd attended St. Paul's preparatory school in Concord, New Hampshire before majoring in philosophy at the prestigious Haverford College in Pennsylvania. The acting bug bit when he went to watch a friend's audition and was obliged to audition in order to stay. He won the role.
After graduation, Judd headed for New York City and the Stella Adler Conservatory where he was believable in the role as the "street-smart Eddie Keaton" in the comedy Making the Grade (1984). Judd's next film role was as the stodgy ROTCer, Phil Hicks, in the ensemble comedy Fandango (1985). Important and diverse roles in the brat-pack films The Breakfast Club (1985) and St. Elmo's Fire (1985) quickly followed. With his privileged upbringing, Judd could have brought the right degree of preppy-smarmyness, (ala James Spader), to any number of vapid roles, but his intense stare and dark smoldering looks gave him a hint of danger which added to his credibility in films like the Billionaire Boys Club (1987) (TV), From the Hip (1987) and New Jack City (1991).
While Judd's career has been peppered with under-promoted films and poorly-written TV appearances, critics have not been overly kind to this misunderstood actor.