Games like The Night Gym
Games like The Night Gym include MiSide, Outlast, Poppy Playtime, Outlast 2, and No, I'm not a Human. We matched them by the tags players give The Night Gym on Steam (Idler, Horror, RPG, Atmospheric, and Psychological Horror): closest matches first, and among equally close ones the better-known games.

MiSide
Shared: Psychological Horror · Horror · Atmospheric

Outlast
Shared: Horror · Atmospheric · Psychological Horror

Poppy Playtime
Shared: Horror · Psychological Horror · First-Person

Outlast 2
Shared: Horror · Psychological Horror · Atmospheric

No, I'm not a Human
Shared: Horror · Psychological Horror · Atmospheric

SOMA
Shared: Horror · Atmospheric · Psychological Horror

Garten of Banban
Shared: Horror · Psychological Horror · First-Person

Five Nights at Freddy's
Shared: Horror · Psychological Horror · Indie

Subliminal
Shared: Psychological Horror · Atmospheric · Horror

Layers of Fear (2016)
Shared: Horror · Atmospheric · Psychological Horror

Mouthwashing
Shared: Horror · Psychological Horror · Atmospheric

Buckshot Roulette
Shared: Horror · First-Person · Dark

From The Darkness
Shared: Horror · Psychological Horror · Atmospheric

Backrooms: Escape Together
Shared: Horror · Psychological Horror · Atmospheric

Visage
Shared: Horror · Psychological Horror · Atmospheric

Phasmophobia
Shared: Horror · Psychological Horror · First-Person

Amnesia: The Dark Descent
Shared: Horror · Psychological Horror · Atmospheric

Lethal Company
Shared: Horror · First-Person · Psychological Horror

Little Nightmares
Shared: Horror · Atmospheric · Psychological Horror

Welcome to Kowloon
Shared: Horror · Atmospheric · Psychological Horror

Five Nights at Freddy's 2
Shared: Horror · Psychological Horror · First-Person

OMORI
Shared: Psychological Horror · RPG · Horror

Firework
Shared: Horror · Psychological Horror · Atmospheric

Iron Lung
Shared: Horror · Atmospheric · Psychological Horror