A native of Wichita, Kansas and of Czech descent, Strnad was influenced by such writers as Mark Twain and John Steinbeck, as well as DC and Marvel comic books.
He was active in comics fandom in the 1960s and contributed to fanzines such as Rocket's Blast Comicollector, where he wrote the column "Eyeing the Egos". He also published his own zine, Anomaly, until it was taken over by Bud Plant.
Strnad's first professional comics were collaborations with Richard Corben, published in Rip Off Press's Fantagor. Other collaborations were published by Warren Publishing. In 1978–1979 he and Corben serialized "New Tales of the Arabian Nights" in Heavy Metal, and in 1982 they produced the Jeremy Brood trade paperback. In 1990, Strnad and Corben produced the five-issue limited series Son of Mutant World, published by Corben's Fantagor Press imprint. From 1996–1997, Strnad and Corben produced "Denz" stories for Penthouse Comix #15–20. Strnad and Corben worked together on the Flash animation web series Bludd for PirateNet in 2000. Dark Horse Comics published Strnad and Corben's limited series RageMoor in 2012.
Strnad has also collaborated a number of times with artist Dennis Fujitake, in Dalgoda, published by Fantagraphics from 1984–1986 (Fantagraphics' first direct-market title), followed by Flesh and Bones (also featuring Dalgoda) in 1986; and Keith Laumer's Retief, published by Mad Dog Graphics in 1987–1988. From 1981–1986, Strnad contributed articles to The Comics Journal.
Other notable titles by Strnad include the Sword of the Atom limited series, with artist Gil Kane, published by DC Comics in 1983, followed by three Specials (1984–1988); Stalkers (Epic Comics, 1990–1991) with Val Mayerik; and Starship Troopers: Dominant Species #1-4 (Dark Horse, 1998) with artist Davide Fabbri.
Strnad's Star Wars work includes story arcs in Star Wars: X-Wing Rogue Squadron (1996–1997), Star Wars: Prelude to Rebellion (1998–1999), and "Vow of Justice" in Star Wars: Republic, all published by Dark Horse Comics.
In the early 1990s, Strnad moved to Los Angeles to join the staff of Disney Television Animation, where he worked on Goof Troop (1992–1993) and Aladdin (1994–1995). He later wrote for Sitting Ducks (Universal, 2001–2003) and Harold and the Purple Crayon (Sony, 2002).
Since 2000, he has concentrated on prose novels, three of which he self-published.
Strnad's wife's name is Julie; he has a step-son. He and his wife live in Los Angeles.
Strnad won the 1970 Goethe Award for "Favorite Fan Writer." He was nominated for the same award in 1972.