Commanding a Mobile Advisory Team during the Vietnam War, he was critically wounded in action and pronounced dead, in 1969, but survived.

After recovering from the injuries, Smallwood moved to New York City where he studied acting at the Neighborhood Playhouse and established a career as a performer in Broadway productions (Mahalia), films and television.

His films include The Cotton Club (1984), Contact (1997), Deep Impact (1998), Larry David's Sour Grapes, Traffic (2000), The One (2001), Quigley (2003), Spectres (2004) and Embers (2015).

On television, he has been a regular and made guest appearances on many series, including Space: Above and Beyond, Millennium, Babylon 5, The X-Files, Curb Your Enthusiasm, Seinfeld, Murphy Brown, Star Trek: Voyager, Star Trek: Enterprise, Friends and The Sarah Silverman Program.

In 2006, the mp3 version of Return to Eden was first runner-up in the audio/spoken word category at the Fifth Annual DIY Book Festival, which celebrates independent authors and publishers.