The game was released in February 2016 for Linux, OS X, PlayStation 4, Windows, and Xbox One in September 2016, and for Nintendo Switch in December 2018.

[3] Through exploration of the surrounding area, Henry uncovers clues about mysterious occurrences in the vicinity that are related to the ransacking of his tower while he is out on a routine patrol and a shadowy figure that occasionally appears watching him from afar.

[8] In the spring of 1989, after his wife Julia (Larissa Gallagher) develops early-onset dementia, Henry (Rich Sommer) takes a job as a fire lookout in Shoshone National Forest, Wyoming.

On his first day, Delilah (Cissy Jones), a lookout in another watchtower, contacts him via walkie-talkie and asks him to investigate illegal fireworks by the lake.

Henry discovers a pair of teenage girls, Chelsea (Erin Yvette) and Lily (Nikki Rapp), who accuse him of leering.

While out hiking, Henry finds an old backpack and a disposable camera belonging to a boy named Brian Goodwin, who Delilah explains was the son of Ned (Mac Brandt), a former lookout.

Ned was an outdoorsman who drank heavily due to his traumatic experiences in the Vietnam War, while his son, Brian, enjoyed fantasy novels and role-playing games.

Determining that the boy died trying to climb the cave, Henry finds a way outside and reports Brian's death to Delilah who becomes upset by the news.

The next day, an evacuation order is given for all the lookouts, as the wildfire that Henry had spotted earlier has grown out of control after merging with the government camp fire.

Henry finds Ned's makeshift bunker, along with items stolen from the government camp, the lookout towers, and the teenage girls, who Delilah confirms have been found safe.

The government camp was simply studying wildlife; Ned had been using its radio equipment to ensure that no one was looking for him and to create transcripts to scare Henry away.

[11] In creating the painting, Moss emulated National Park Service posters from the New Deal era in both color palette and iconography.

[16] The in-game fire lookout towers were built in accordance with government specifications, utilizing standard lumber size, after Ng's first attempt was unsatisfactory.

[17] The walkie-talkie interaction in Firewatch is inspired by the relationship in BioShock between the player character and Atlas, as well as the dialog system from The Walking Dead.

[11] At one point in the development, it was intended that the protagonist would be able to communicate with multiple characters, such as hikers, but the idea was discarded due to its expense and the schedule requirements with which the team were working.

It took longer to find a voice actor for Henry whom the developers felt jibed with Jones; they ultimately cast Rich Sommer.

[18][19] The game's opening chapter features the song "Push Play" from Joy Chun and Nate Bosley's 2014 synthwave album Let's Get Electric, which depicts a fictitious 1980s synthpop act known as Cheap Talk.

[5] At GDC, Campo Santo housed a public playtest, and Ng hosted a panel on the design and aesthetic of the game entitled "The Art of Firewatch".

[26] Users of the HTC Vive and Oculus Rift virtual reality headsets can tour Henry's lookout tower using the Steam application Destinations.

[31][32] 4,800 copies were made available for order on the Limited Run Games website on December 16, 2016, while 2,500 were sold through the Campo Santo online store starting January 16, 2017.

[41] Scott Butterworth of GameSpot thought that the analog navigation tools – a hand-held compass and paper map – were "immersive" but "occasionally frustrating".

He found the visual beauty of the setting allowed for a more rewarding form of exploration and noted that the sound design complemented the depth of its atmosphere.

Judging the development of the characters through dialog to be "bold" and "admirable", he opined that it served as "a patient, reflective examination of how two people grow to trust and care for each other".

[44] Polygon's Colin Campbell appreciated the use of humor and empathy to develop the characters, considered the game's mystery to be successful and the story to be "elegant" and "satisfying".

[45] On August 17, 2020, it was announced that Campo Santo was partnering with production company Snoot Entertainment (Keith Calder and Jess Wu) to adapt the game into a feature film.