Turtledove was born in Los Angeles, California on June 14, 1949, and grew up in Gardena, California. His paternal grandparents, who were Romanian Jews, had first emigrated to Winnipeg, Manitoba, before moving to the U.S. and California.  He was educated in local public schools in early life.
After dropping out during his freshman year at Caltech, Turtledove attended UCLA, completing his undergraduate degree and receiving a Ph.D. in Byzantine history in 1977. His dissertation was titled The Immediate Successors of Justinian: A Study of the Persian Problem and of Continuity and Change in Internal Secular Affairs in the Later Roman Empire During the Reigns of Justin II and Tiberius II Constantine (AD 565–582). 
In 1979, Turtledove published his first two novels, Wereblood and Werenight, under the pseudonym "Eric G. Iverson." Turtledove later explained that his editor at Belmont Tower did not think people would believe the author's real name was "Turtledove" and came up with something more Nordic.  He continued to use the "Iverson" name until 1985. Another early pseudonym was "Mark Gordian."
That year he published Herbig-Haro and And So to Bed under his real name. Turtledove has recently begun publishing historical novels under the pseudonym "H.N. Turteltaub" (Turteltaube means turtle dove in German).  He published three books as Dan Chernenko (the Scepter of Mercy series).
He has written several works in collaboration, including The Two Georges with Richard Dreyfuss, "Death in Vesunna" with his first wife, Betty Turtledove (pen-name, Elaine O'Byrne); Household Gods with Judith Tarr; and others with Susan Shwartz, S.M. Stirling, and Kevin R. Sandes.
Turtledove won the Homer Award for Short Story in 1990 for "Designated Hitter," the John Esten Cooke Award for Southern Fiction in 1993 for The Guns of the South, and the Hugo Award for Novella in 1994 for "Down in the Bottomlands." Must and Shall was nominated for the 1996 Hugo Award and Nebula Award for Best Novelette; it received an honorable mention for the 1995 Sidewise Award for Alternate History. The Two Georges also received an honorable mention for the 1995 Sidewise Award for Alternate History.
His Worldwar series received a Sidewise Award for Alternate History Honorable Mention in 1996. In 1998, his novel, How Few Remain, won the Sidewise Award for Alternate History. He won his second Sidewise Award in 2003 for his novel Ruled Britannia. 
Publisher's Weekly dubbed Turtledove "The Master of Alternate History".  Within that genre, he is known for creating original alternate history scenarios, such as survival of the Byzantine Empire or an alien invasion in the middle of the Second World War. In addition, he has been credited with giving original treatment to alternate themes previously dealt with by many others, such as the victory of the South in the American Civil War or the victory of Nazi Germany in the Second World War. His novels have been credited with bringing alternate history into the mainstream.  He bases his alternate history in scenes of military combat and warfare.