He is known for the Bolo and Retief stories. Stories from the former chronicle the evolution of super tanks that eventually become self-aware through the constant improvement resulting from centuries of intermittent warfare against various alien races. The latter deals with the adventures of a cynical spacefaring diplomat who constantly has to overcome the red-tape-infused failures of people with names like Ambassador Grossblunder. The Retief stories were greatly influenced by Laumer''s earlier career in the US Foreign Service. In an interview with Paul Walker of Luna Monthly, Laumer states "I had no shortage of iniquitous memories of the Foreign Service."

In addition to his Bolo and Retief stories, Laumer''s more serious adventures included the subjects of time travel and alternate-world adventures such as found in his The Other Side of Time, A Trace of Memory, and Dinosaur Beach.

Four of his shorter works received Hugo or Nebula Award nominations ("In the Queue", was nominated for both) and his novel A Plague of Demons (1965) received a nomination for the Nebula Award for Best Novel in 1966.

His Bolo creations are considered a major early influencer of the military science fiction sub-genre, and many well known military science fiction authors have written stories in tribute to this original.

An anthology "Created by Keith Laumer", Dangerous Vegetables, appeared in 1998. Actually edited by Martin H. Greenberg and Charles G. Waugh, the book''s introduction (by Ben Bova) said the book was Laumer''s idea but that he had died without completing it.