Kzinti evolved from a plains hunting felid on a slightly colder, drier planet than Earth. The Kzin word for their home planet translates as Homeworld. The world is often known as Kzinhome by the Kzinti themselves. The Kzin home world is the third planet orbiting the star 61 Ursae Majoris.

The Kzin civilization was at an iron-age technological level when an alien race called the Jotok landed and made stealthy First Contact with a tribe of primitive hunter/gatherer Kzinti. The Jotok were interstellar merchants looking for a species they could use as mercenaries.

Once the Jotok had taught the Kzinti how to use high-technology weapons and other devices (including spacecraft), the Kzin rebelled and made their former masters into slaves, as well as the occasional meal. The crest of the Riit (Royal) family appears to be a bite mark, but is in fact a dentate leaf, with the words "From mercenary to master." written around it in Kzinti script.

Kzin society is extremely male dominated. The leader of the race is called the Patriarch, which is a hereditary title. The Kzinti call themselves "Heroes" or the "Heroes Race" and because they believe themselves to be "heroes", their society places a very high value on "acting Heroic" and behaving in a heroic fashion.

To Kzin society, "heroic" means being honorable and having integrity. Kzin honor is similar in many ways to the samurai code of Bushido. Strakh serves as almost a sort of currency or favour system, since they do not use money in their culture. For example, if the Patriarch gets meat from a sellers' market stand, the seller gains considerable strakh which will bring honour to the seller allowing him to get better customers - which leads to more strakh, which gives the seller a higher status within the community.

Once Kzinti gained access to genetic-manipulation technology, they started manipulating themselves in order to bring out the most "heroic" qualities and recede undesired ones. To this end, because females are not valued except as bearers of children, the male-dominated Kzin society bred (most of) their own females into sub-sapience.

Kzinti are often described as anthropomorphic tigers, but there are significant and visible differences. Kzinti are larger than humans, standing around 8 feet (2.4 m) tall and weighing around 500 pounds (230 kg). These tiger-sized bipeds have large membranous ears, a barrel-chested torso with a flexible spine, and large fangs and claws. One human gave an apt description of Kzin as "eight feet of death."