Maguire was born in Albany, New York. He received his B.A. from the State University of New York at Albany and his Ph.D. in English and American Literature from Tufts University. He was a professor and co-director at the Simmons College Center for the Study of Children's Literature from 1979-1985. In 1987 Maguire co-founded Children's Literature New England Gregory Maguire &- Harper Collins Publishers. He still serves as co-director of CLNE, although that organization has announced its intention to close after its 2006 institute. Childrens Literature New England He is also a board member of the National Children's Book and Literacy Alliance The National Children's Book and Literacy Alliance a national not-for-profit that actively advocates for literacy, literature, and libraries.

Maguire is married to painter Andy Newman. They have adopted three children, two from Cambodia and one from Guatemala.

For children

• The Lightning Time (1978)
• The Daughter of the Moon (1980)
• Lights on the Lake (1981)
• The Dream Stealer (1983)
• I Feel like the Morning Star (1989)
• Lucas Fishbone (1990)
• Missing Sisters (1994)
• "The Honorary Shepherds", in Am I Blue?: Coming Out From the Silence
• Oasis (1996)
• The Good Liar (1997)
• "Beyond the Fringe", in A Glory of Unicorns
• Crabby Cratchitt (2000)
• Leaping Beauty: And Other Animal Fairy Tales (2004)
• Hamlet Chronicles
• Seven Spiders Spinning (1994)
• Five Alien Elves (1998)
• Six Haunted Hairdos (1999)
• Four Stupid Cupids (2000)
• Three Rotten Eggs (2002)
• A Couple of April Fools (2004)
• One Final Firecracker (2005)
• What-the-Dickens: The Story of a Rogue Tooth Fairy (2007)

For adults

• The Wicked Years
• The Life and Times of the Wicked Witch of the West (1995)
• Son of a Witch (2005)
• A Lion Among Men (2008)
• Out of Oz (working title) (release date to be announced)
• Confessions of an Ugly Stepsister (1999)
• Lost (2001)
• Mirror, Mirror (2003)
• The Next Queen of Heaven (2010)

Short stories

• Scarecrow (2001), published in Half-Human
• Fee, Fie, Foe et Cetera (2002), published in The Green Man: Tales from the Mythic Forest
• The Oakthing (2004), published in The Faery Reel: Tales from the Twilight Realm
• Chatterbox, published in I Believe in Water: Twelve Brushes With Religion
• The Honorary Shepards (1994), published in Am I Blue?:Coming Out From The Silence
• Beyond the Fringe (1998) published in A Glory of Unicorns
• The Seven Stage a Comeback (2000) published in A Wolf at the Door and Other Retold fairy Tales
• A Christmas Story (2009)
• The Silk Road Runs Through Tupperneck, N.H. (2009), published in Twelve Stories of Identity

Non-fiction

• Making Mischief: A Maurice Sendak Appreciation (2009)