Games like Ward 9
Games like Ward 9 include Firewatch, What Remains of Edith Finch, SOMA, Layers of Fear (2016), and Mouthwashing. We matched them by the tags players give Ward 9 on Steam (Psychological Horror, Horror, First-Person, Atmospheric, and Singleplayer): closest matches first, and among equally close ones the better-known games.

Firewatch
Shared: Atmospheric · First-Person · Story Rich

What Remains of Edith Finch
Shared: Atmospheric · Story Rich · First-Person

SOMA
Shared: Psychological Horror · Horror · Atmospheric

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

Mouthwashing
Shared: Psychological Horror · Horror · Atmospheric

Amnesia: A Machine For Pigs
Shared: Horror · Psychological Horror · Atmospheric

MiSide
Shared: Psychological Horror · Horror · First-Person

Still Wakes the Deep
Shared: Psychological Horror · Horror · First-Person

Outer Wilds
Shared: Exploration · Story Rich · Atmospheric

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

Poppy Playtime
Shared: Horror · Singleplayer · First-Person

Outlast
Shared: Horror · First-Person · Psychological Horror

ROUTINE
Shared: Psychological Horror · Singleplayer · Atmospheric

The Park®
Shared: Psychological Horror · Horror · First-Person

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

KARMA: The Dark World
Shared: Psychological Horror · Horror · First-Person

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

Visage
Shared: Psychological Horror · Horror · First-Person

Sally Face - Episode One
Shared: Psychological Horror · Horror · Story Rich

Outlast 2
Shared: Psychological Horror · Horror · First-Person

SILENT HILL 2
Shared: Psychological Horror · Horror · Atmospheric

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

Blair Witch
Shared: Horror · Psychological Horror · First-Person

Little Nightmares II
Shared: Horror · Singleplayer · Psychological Horror