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, when he published his "Herbig-Haro" and "And So to Bed" under his real name. Another early pseudonym was "Mark Gordian." 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).

Throughout the late 1970s and early 1980s, Turtledove worked as a technical writer for the Los Angeles County Office of Education. In 1991, he left the LACOE and turned to writing full time. From 1986 to 1987, he served as the Treasurer for the Science Fiction Writers of America.

He has written several works in collaboration, including The Two Georges with Richard Dreyfuss, "Death in Vesunna" with his first wife 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, the Hugo Award for Novella in 1994 for "Down in the Bottomlands." "Must and Shall" was nominated for the 1996 Hugo Award for Best Novelette, the 1996 Nebula Award for Best Novelette and 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. The Worldwar series received a Sidewise Award for Alternate History Honorable Mention in 1996. In 1998, the novel How Few Remain won the Sidewise Award for Alternate History. He won his second Sidewise Award in 2003 for the novel Ruled Britannia. On August 1, 1998, Turtledove was named honorary Kentucky Colonel while Guest of Honor at Rivercon XXIII in Louisville, Kentucky. The Gladiator was the co-winner of the 2008 Prometheus Award.

Turtledove served as the toastmaster for Chicon 2000, the 58th World Science Fiction Convention.

He is married to mystery and SF writer Laura Frankos. His brother-in-law is fantasy author Steven Frankos. He has three daughters: Alison, Rachel and Rebecca.

Turtledove has been dubbed "The Master of Alternate History". Within that genre he is known both 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 and for giving a fresh and original treatment to themes previously dealt with by many others, such as the victory of the South in the American Civil War and of Nazi Germany in the Second World War. His novels have been credited with bringing alternate history into the mainstream. His style of alternate history has a strong military theme with scenes of combat happening throughout many of his works.

Fantasy series about a world that is analogous to the Byzantine Empire.

Science Fiction/Alternate History — Aliens invade in the middle of World War II

Alternate History — The South has won the American Civil War; this posits what would then happen over the next century. (The series consists of several smaller series and has no official title)