Games like Unseen
Games like Unseen include Summer of '58, Mouthwashing, Layers of Fear (2016), SOMA, and What Remains of Edith Finch. We matched them by the tags players give Unseen on Steam (Psychological Horror, Horror, Exploration, Simulation, and Atmospheric): closest matches first, and among equally close ones the better-known games.

Summer of '58
Shared: Horror · Psychological Horror · Atmospheric

Mouthwashing
Shared: Psychological Horror · Horror · Atmospheric

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

SOMA
Shared: Psychological Horror · Horror · Atmospheric

What Remains of Edith Finch
Shared: Atmospheric · Exploration · Walking Simulator

September 7th
Shared: Horror · Exploration · Psychological Horror

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

DON'T SCREAM
Shared: Psychological Horror · Horror · Atmospheric

Psalm 5:9-13
Shared: Psychological Horror · Horror · Exploration

Amnesia: A Machine For Pigs
Shared: Horror · Psychological Horror · Walking Simulator

MiSide
Shared: Psychological Horror · Horror · First-Person

Fears to Fathom - Ironbark Lookout
Shared: Psychological Horror · Horror · Atmospheric

Firewatch
Shared: Atmospheric · Walking Simulator · Exploration

Lethal Company
Shared: Horror · Psychological Horror · Exploration

Scanner Sombre
Shared: Exploration · Horror · Walking Simulator

Don't Play This
Shared: Psychological Horror · Horror · Exploration

The Exit 8
Shared: Exploration · Horror · Psychological Horror

Visage
Shared: Psychological Horror · Horror · First-Person

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

Outlast
Shared: Horror · Psychological Horror · Atmospheric

Still Wakes the Deep
Shared: Psychological Horror · Horror · Walking Simulator

Phasmophobia
Shared: Horror · Psychological Horror · First-Person

Iron Lung
Shared: Horror · Psychological Horror · Atmospheric

Father's Day
Shared: Psychological Horror · Simulation · Indie