In 2298, the science scout USS Bluford intercepted several subspace communications bursts in a heretofore unknown language while on routine patrol. Years later, these were discovered to be from a Tzenkethi ship. (Star Trek: Avenger: "Nearly a Valediction")
The United Federation of Planets and Tzenkethi fought a war during the 24th century. The USS Okinawa, under the command of Captain James Leyton, fought against a number of Tzenkethi raiders during this war. (DS9: "The Adversary", "Homefront")
En route to head off the Tzenkethi during the war in 2360, the USS Cartwright, under the command of Captain Sydney Caldwell, went missing and was presumed destroyed. (Star Trek: The Cantabrian Expeditions: "Breaking Benjamin", "Bitter Sweet") One of the officers to distinguish himself during the conflict was an Admiral named Bartholomew Thomas. (Star Trek: Outpost)
- No "official" dates were pegged down for the Federation-Tzenkethi War, but for Star Trek: The Cantabrian Expeditions, the author came up with the year 2360 as being a year in which the war took place. This would allow for Benjamin Sisko to have his promotion to lieutenant commander and first officer aboard the Okinawa before his assignment as first officer aboard the USS Saratoga and explains why the war was never mentioned on Star Trek: The Next Generation.
In late 2371, Federation ambassador Krajensky told Deep Space 9 Captain Benjamin Sisko the Tzenkethi Autarch has been deposed. In response, the USS Defiant was to proceed to the Federation-Tzenkethi border, reinforcing the Federation presence to the new leading faction. Investigation en route led the Dominion had engineered the mission to start another war between the Federation and Tzenkethi. No coup d'etat had taken place on Tzenketh. This Krajensky was, in fact, a Founder, who attempted to commandeer the Defiant to attack a Tzenkethi settlement on M'kemas III. The Founder was stopped before the Defiant could reach the planet. (DS9: "The Adversary")
- Captain Sisko stated in "The Adversary" a line implying there have been more than one war between the Tzenkethi and Federation, but this could have been a script error or implying there were skirmishes or several periods to the same war.
Because their participation in the Generation War left the Coalition in an economic crisis, the Tzenkethi banking system was on the verge of collapse, because, unlike Romulans, they had no real estate bubble to fuel their recovery. In a last-ditch attempt to recover, a Tzenkethi-led banking consortium wagered the entirety of the consortium on a hockey game in hopes of taking over Bouteina Holdings. However, their plan failed when the Praetorians scored in overtime, leading to the game ending 9-8. (RIS Bouteina: "Ultimate Wager")
In 2410, the Tzenkethi battleship CSS Cortisgor attempted to threaten the First Federation world Carpi but, when confronted by the USS Ragnarok, was warned against it and the confrontation itself by alternate future versions of each ship's Captains. (Star Trek: Phoenix-X: "Enmity")
In 2412, the Tzenkethi were found to be backing the Cardassian Third Empire extremist group. A force of Tzenkethi, including special-forces officer Warram Tzen-Gravu, attempted to aid Gul Kerim Morag at his last stand at Setok Nor, but was defeated; Tzen-Gravu was killed by Lieutenant Rachel Connor. (Bait and Switch: "Live, not Survive")
- It is often assumed that Tzenkethi was intended to be a near-anagram for the Kzinti from Larry Niven's Known Space universe and TAS: "The Slaver Weapon". Robert Hewitt Wolfe has stated that he believes that he formed the name by Kzinti with Tsankth, a race from the RuneQuest and HeroQuest RPGs. Wolfe also said he did not picture them as cats like the Kzinti, but saw the Tzenkethi as being "heavily-armored lizard things". 
- Star Trek: Liberty assumes the Tzenkethi are felinoid, replacing the Kzinti in that continuity. In Orion Press continuity, the Tzenkethi and the Kzin are the same felinoid species. In Star Trek: Pendragon and RIS Bouteina, however, the Tzenkethi are reptilian.
- In the continuity established by the Pocket Books novels, the Tzenkethi are a more-or-less humanoid species with a limited skeletal structure and mostly-fluidic, highly-flexible, bioluminescent bodies. The were founding members of the Typhon Pact.