He married Marilyn Joyce 'Fuzzy Pink' Wisowaty, herself a well-known science fiction and Regency literature fan, on September 6, 1969. He has since lived in Los Angeles suburbs, including Chatsworth and Tarzana, as a full-time writer. He did a year of graduate work in mathematics at the University of California at Los Angeles. He briefly attended the California Institute of Technology and graduated with a Bachelor of Arts in mathematics (with a minor in psychology) from Washburn University, Topeka, Kansas, in 1962. In fact, much of his writing since the 1970s has been in collaboration, particularly with Pournelle, Steven Barnes, Brenda Cooper, or Edward M. He co-authored a number of novels with Jerry Pournelle.

Niven created an alien species, the Kzin, which were featured in a series of twelve collection books, the Man-Kzin Wars. His fantasy includes The Magic Goes Away series, which utilizes an exhaustible resource, called Mana, to make the magic a non-renewable resource. Niven also often includes elements of detective fiction and adventure stories. The creation of thoroughly worked-out alien species, which are very different from humans both physically and mentally, is recognized as one of Niven's main strengths.

His work is primarily hard science fiction, using big science concepts and theoretical physics. Laurence van Cott Niven's best known work is Ringworld(Ringworld, #1) (1970), which received the Hugo, Locus, Ditmar, and Nebula awards.

Ringworld throne