Games like Split Brain
Games like Split Brain include Escape the Backrooms, Phasmophobia, We Were Here Forever, We Were Here, and Inside the Backrooms. We matched them by the tags players give Split Brain on Steam (Online Co-Op, Escape Room, 3D, Puzzle Platformer, and Adventure): closest matches first, and among equally close ones the better-known games.

Escape the Backrooms
Shared: Online Co-Op · Horror · Multiplayer

Phasmophobia
Shared: Online Co-Op · Horror · Multiplayer

We Were Here Forever
Shared: Online Co-Op · Escape Room · 3D

We Were Here
Shared: Escape Room · Co-op · Horror

Inside the Backrooms
Shared: Horror · Online Co-Op · Multiplayer

We Were Here Too
Shared: Online Co-Op · Escape Room · Horror

PEAK
Shared: Online Co-Op · Multiplayer · Adventure

The Past Within
Shared: Online Co-Op · Escape Room · Co-op

We Were Here Together
Shared: Online Co-Op · Escape Room · Puzzle

R.E.P.O.
Shared: Online Co-Op · Horror · Multiplayer

It Takes Two
Shared: Online Co-Op · Multiplayer · Co-op

Backrooms: Escape Together
Shared: Online Co-Op · Horror · Multiplayer

Demonologist
Shared: Online Co-Op · Horror · Multiplayer

Dead by Daylight
Shared: Online Co-Op · Horror · Multiplayer

Labyrinthine
Shared: Online Co-Op · Horror · Multiplayer

Pacify
Shared: Online Co-Op · Horror · Multiplayer

Lethal Company
Shared: Online Co-Op · Horror · Co-op

Escape Simulator
Shared: Escape Room · Online Co-Op · Multiplayer

DEVOUR
Shared: Online Co-Op · Horror · Multiplayer

Little Nightmares II
Shared: Adventure · Horror · Puzzle Platformer

RV There Yet?
Shared: Online Co-Op · Multiplayer · Adventure

Chained Together
Shared: Adventure · Online Co-Op · Co-op

Little Nightmares III
Shared: Adventure · Online Co-Op · Horror

Scarlet Idol
Shared: Online Co-Op · Multiplayer · Co-op