The 51st Writers Guild of America Awards, given in 1999, honored the film and television best writers of 1998.

Film

Best Adapted Screenplay

Out of Sight – Scott Frank

• A Civil Action – Steven Zaillian
• Gods and Monsters – Bill Condon
• Primary Colors – Elaine May
• A Simple Plan – Scott B. Smith

Best Original Screenplay

Shakespeare in Love – Marc Norman and Tom Stoppard

• Bulworth – Warren Beatty and Jeremy Pikser
• The Opposite of Sex – Don Roos
• Saving Private Ryan – Robert Rodat
• The Truman Show – Andrew Niccol

Television

Best Episodic Drama

"Proofs for The Existence of God" – Nothing Sacred – Paul Leland

• "Exodus" – ER – Walon Green and Joe Sachs
• "Apollo One" – From the Earth to the Moon – Graham Yost
• "Finnegan's Wake" – Homicide: Life on the Street – David Mills, James Yoshimura and David Simon
• "Saigon Rose" – Homicide: Life on the Street – Eric Overmyer
• "The Subway" – Homicide: Life on the Street – James Yoshimura
• "Burned" – Law & Order – Siobhan Byrne
• "Betrayal" – The Practice – David E. Kelley
• "The Marie Taquet Story" – Rescuers: Stories of Courage: Two Couples – Cy Chermak, Francine Carroll and Malka Drucker

Best Episodic Comedy

"Frasier's Imaginary Friend" – Frasier – Rob Greenberg

• "Pilot" – Dharma & Greg – Dottie Dartland and Chuck Lorre
• "Emma" – Ellen – Lawrence Broch
• "Never Can Say Goodbye" – Murphy Brown – Diane English

Best Long Form – Adapted

The Love Letter – James S. Henerson

• Don King: Only in America – Kario Salem
• Thicker Than Blood – Bill Cain