Turtle Rock Studios is an American video game developer based in Lake Forest, California, founded in March 2002 by Mike Booth alongside Phil Robb and Chris Ashton. The studio came up with the original Left 4 Dead concept and developed it with Valve, then built the asymmetrical monster hunting shooter Evolve for 2K Games. In 2021 it returned to co-op zombie shooters with Back 4 Blood, published by Warner Bros. Games. Valve bought Turtle Rock in 2008 and ran it as Valve South before closing it, and the remaining team reformed Turtle Rock as an independent studio in March 2010. Tencent acquired Turtle Rock Studios through its parent company Slamfire Inc. in December 2021, and the studio has been working on an unannounced project since ending Back 4 Blood content in early 2023.
Booth, Robb, and Ashton all came out of Westwood Pacific, where they worked on real-time strategy games including Command & Conquer: Red Alert 2. Ashton left first, joining the Counter-Strike mod team as a texture artist and following it to Valve after Valve bought the mod. Booth and Robb stayed on through Command & Conquer: Yuri's Revenge and Command & Conquer: Generals, then left after Electronic Arts absorbed Westwood, with Robb later saying the acquisition stripped the studio of its personality. Booth founded Turtle Rock in 2002 with a team of about six people working out of his garage, and the studio took its name from the Irvine neighborhood where he lived.
Valve brought the young studio in to work on Counter-Strike: Condition Zero, which shipped in 2004 through Sierra Entertainment. Turtle Rock also handled the 2003 Xbox port of Counter-Strike for Microsoft Game Studios, then moved on to Counter-Strike: Source and Half-Life 2: Deathmatch. The bot AI the team built for Condition Zero became the foundation for the AI technology that later powered Left 4 Dead.
After Counter-Strike: Source, Turtle Rock wanted to make a game of its own. The team first prototyped a first-person wizard combat game, then scrapped it as overcomplicated and pivoted to a Counter-Strike mod called Terror-Strike, where players fought knife-wielding bots that behaved like zombies. Every game the studio had worked on up to that point was competitive multiplayer, so the team wanted something built around friends playing together instead of against each other, citing Secret of Mana as an example of that kind of experience. Watching 28 Days Later pushed the idea further, and the zombie mod turned into the pitch that Valve agreed to fund and publish. Development on Left 4 Dead began in 2005, Valve announced the game on November 20, 2006, and it released in November 2008 for Windows and Xbox 360.
Left 4 Dead put four survivors, Bill, Zoey, Louis, and Francis, up against hordes of infected and special infected like the Smoker, Hunter, Boomer, and Tank. Its AI Director adjusted enemy spawns and item drops on the fly based on how the team was playing, so no two runs through a campaign played out the same way. Versus mode handed control of the special infected to a second team of four, with both teams swapping sides between rounds. The PC version holds an 89 on Metacritic, and the Left 4 Dead series, counting Valve's Left 4 Dead 2, had sold 12 million copies by October 2012.
Valve bought Turtle Rock on January 10, 2008, before Left 4 Dead shipped, and renamed it Valve South. Gabe Newell called the purchase an easy decision at the time, pointing to Valve's high expectations for the game and the long relationship between the two companies.
Between nine and 11 Turtle Rock employees relocated to Valve's Seattle headquarters after the acquisition, which left Valve South too small in Valve's view to operate as a AAA studio. Coordinating with a satellite team in Southern California also proved difficult for Valve. Turtle Rock, for its part, felt communication with Valve was lacking and grew frustrated with how slowly projects moved. Newell proposed splitting the two, and Valve South closed after Left 4 Dead shipped. Valve kept the Left 4 Dead franchise and let the original team use the Turtle Rock name and logo again, which Valve's Doug Lombardi confirmed on June 3, 2009.
Robb and Ashton relaunched Turtle Rock Studios as an independent company on March 17, 2010, with about 13 people on staff. The two co-founders ended up sharing the studio head role, with Ashton initially turning it down, and both have described themselves as developers first rather than managers. Booth eventually moved on and later became chief creative officer at J.J. Abrams' Bad Robot Games. Valve kept the reformed studio busy with contract work on post-launch content for Left 4 Dead and Left 4 Dead 2, including The Sacrifice, and Turtle Rock also worked on Counter-Strike: Global Offensive during its early development. In June 2010 the studio opened Turtle Rock Garage, a small division for casual and experimental games that released the mobile game Leap Sheep! that year.
The idea behind Evolve actually predated Left 4 Dead. Turtle Rock took the asymmetrical feel of Left 4 Dead's Versus mode and crossed it with hunting games like Cabela's Big Game Hunter, building toward a game where the prey could fight back. Publishers including Valve passed on the pitch, with several doubting a studio Turtle Rock's size could handle a AAA project. THQ took the chance, announcing in May 2011 that it would publish Turtle Rock's next game, and Robb treated the project as the studio's proving ground, a chance to show Turtle Rock was more than a Valve support team.
THQ declared bankruptcy on December 19, 2012, and Evolve went up for auction alongside the publisher's other unannounced projects. Turtle Rock tried to buy back its own game with a $250,000 bid that Ashton described as everything the studio had in the bank, and Take-Two Interactive outbid it with $11 million for the game and the rights to the franchise.
Game Informer revealed Evolve on January 7, 2014, and the team grew to around 75 people during production. 2K Games pushed the release from October 2014 to February 10, 2015, when Evolve launched on Windows, PlayStation 4, and Xbox One. Four players took on hunters like Markov, Hank, Val, and Griffin in first-person, while a fifth player controlled a monster like the Goliath, Kraken, or Wraith in third-person, feeding and evolving into stronger stages before the final fight. Evolve won Best of Show at the 2014 Game Critics Awards, reviewed well at launch, and shipped 2.5 million copies by May 2015, with Take-Two calling it a permanent IP for the company. The pile of DLC available on day one drew heavy criticism, though, and the player base dropped off quickly.
Turtle Rock relaunched the PC version as the free-to-play Evolve Stage 2 in July 2016, and PC Gamer reported a 16,000 percent jump in players, from a peak of 157 the day before the switch to more than 24,000 after it. The bump did not hold. 2K and Turtle Rock confirmed on October 25, 2016, that development on Evolve had stopped, and 2K shut down the game's dedicated servers on September 3, 2018. Take-Two still owns Evolve, and an Evolve sequel never happened.
Turtle Rock announced a new IP with Perfect World Entertainment in December 2016, but the project was later cancelled when the two companies agreed to part ways. From 2016 through 2019 the studio focused on virtual reality games published by Oculus Studios. Face Your Fears arrived in 2016 as a collection of horror jump scares, followed by The Well on Samsung Gear VR on October 11, 2017. Face Your Fears 2 and the fantasy adventure Journey of the Gods both launched in 2019 for Oculus Quest.
Turtle Rock announced Back 4 Blood in March 2019 with Warner Bros. Games as publisher. Since Valve still owns Left 4 Dead, Back 4 Blood was built as an original IP that plays as a spiritual successor to it. The game released on October 12, 2021, for Windows, PlayStation 4, PlayStation 5, Xbox One, and Xbox Series X|S, launching day one on Xbox Game Pass. Players controlled the Cleaners, survivors like Walker, Holly, Hoffman, Doc, Evangelo, Jim, Karlee, and Mom, fighting the Ridden after the Devil Worm parasite turned most of humanity. The biggest change from Left 4 Dead was the card system, which let each player build a deck of perks and modifiers before a run, while the Game Director played corruption cards that changed the conditions of each level.
Warner Bros. Games and Turtle Rock announced in 2022 that more than 10 million players had played Back 4 Blood, with Warner Bros. calling it 2021's best-selling new IP on consoles. Three expansions followed, with Tunnels of Terror in April 2022, Children of the Worm in August 2022, and River of Blood in December 2022, adding new Cleaners and campaign content. On February 2, 2023, Turtle Rock announced it was ending new content for Back 4 Blood, explaining that the studio was too small to keep supporting the game while spinning up its next project. Online services for Back 4 Blood stayed active.
Tencent announced on December 17, 2021, that it had acquired Slamfire Inc., Turtle Rock's parent company, for undisclosed terms, just two months after Back 4 Blood launched. Turtle Rock stayed autonomous under the deal, with Robb and Ashton continuing to lead the studio. President and general manager Steve Goldstein said Tencent would help the team build the ambitious games it had been dreaming about while letting the studio keep its independence, and Tencent Games chief strategy officer Eddie Chan pointed to Turtle Rock's approach to co-op online games as the draw. The acquisition had no effect on Back 4 Blood, which Warner Bros. Games continued to publish.
Turtle Rock has been working on an unannounced game since early 2023. In March 2023 the studio hired Jared Rosen, previously a principal narrative writer at Riot Games, as narrative director to build that project's universe and story. In 2024, MP1st spotted a project called Gobi 2 on the résumé of actor Jesse Hutch, who previously did motion capture for JD Fenix in Gears of War 4, and linked it to a Back 4 Blood sequel, with a Back 4 Blood 2 website domain also registered the year before. Turtle Rock has not confirmed a Back 4 Blood 2, and as of October 2026 the studio has not officially revealed its next game.