Novels

• The Blackboard Cavalier (1966)
• The Addison Tradition (1968)
• A Long Communion (1974)
• The Humans of Ziax II (1974)
• The Windows of Forever (1975)
• The Extraterritorial (1977)
• The Drought on Ziax II (1978)
• The Juggler (1996)

Del Whitby series

• Starbrat (1972)
• Stardrift (1973; also known as Nail Down the Stars)
• Under a Calculating Star (1975)
• A Law for the Stars (1976)
• Frostworld and Dreamfire (1977)
• The Mansions of Space (1983)

Iron Angel series

• Ironbrand (1980)
• Greymantle (1981)
• Kingsbane (1982)
• The Time of the Annihilator (1985)

Kedrigern series

• A Voice for Princess (1986)
• The Questing of Kedrigern (1987)
• Kedrigern in Wanderland (1988)
• Kedrigern and the Charming Couple (1989)
• A Remembrance for Kedrigern (1990)
• The Domesticated Wizard (2002; omnibus including A Voice for Princess and The Questing of Kedrigern, plus 6 short stories)
• Dudgeon and Dragons (2003; omnibus including Kedrigern in Wanderland and Kedrigern and the Dragon comme il faut-New, plus 8 short stories)

The Apprentice Kedrigern (Young Kedrigern) series

• Young Kedrigern and First Spell^[1] (published only in Czech, 1998)
• Young Kedrigern and Search for the Past^[2] (published only in Czech, 1999)
• Young Kedrigern: The Making of A Wizard (published only in Czech, 2001)

Short fiction

Collections

• Other Stories (1983)

Stories^[3]

• "Autumn Sunshine for Moe Joost" (1979)
• "No More Pencils, No More Books" (1979)
• "The Last Jerry Fagin Show" (1980)
• "A Hedge Against Alchemy" (1981)
• "Final Version" (1982; included in 100 Short Short Fantasy Stories)
• "Stoneskin" (1984)
• "Spirits from the Vasty Deep" (1986)
• "Alaska" (1989)
• "Timekeeper" (1990)
• "A Boy and His Wolf: Three Versions of a Fable" (1993; in the anthology Xanadu)
• "The Persistence of Memory" (1998)
• "Laugh Clone Laugh" (Playboy Magazine, May 1986)
• "Father, Dear Father, Come Home With Me Now" (Dragon Magazine, March 1990, pg. 58)

• John Morressy at the Internet Speculative Fiction Database
• SFWA Obituary at the Wayback Machine (archived May 16, 2008)
• Independent (UK) Obituary. April 1, 2009.