Games like Pierline
Games like Pierline include Mouthwashing, Firewatch, What Remains of Edith Finch, Fears to Fathom - Ironbark Lookout, and Layers of Fear (2016). We matched them by the tags players give Pierline on Steam (Horror, Indie, Psychological Horror, Atmospheric, and Walking Simulator): closest matches first, and among equally close ones the better-known games.

Mouthwashing
Shared: Horror · Psychological Horror · Atmospheric

Firewatch
Shared: Atmospheric · Walking Simulator · Mystery

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

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

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

Firework
Shared: Horror · Indie · Psychological Horror

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

[Chillas Art] The Convenience Store
Shared: Horror · Indie · Psychological Horror

Fears to Fathom - Woodbury Getaway
Shared: Horror · Psychological Horror · Atmospheric

Fears to Fathom® - Scratch Creek
Shared: Horror · Psychological Horror · Indie

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

DREDGE
Shared: Exploration · Atmospheric · Psychological Horror

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

The Park®
Shared: Horror · Psychological Horror · Walking Simulator

Sally Face - Episode One
Shared: Indie · Psychological Horror · Horror

Layers of Fear 2 (2019)
Shared: Horror · Psychological Horror · Indie

SOMA
Shared: Horror · Psychological Horror · Atmospheric

Poppy Playtime
Shared: Horror · Psychological Horror · Indie

Fears to Fathom - Norwood Hitchhike
Shared: Horror · Psychological Horror · Atmospheric

Scanner Sombre
Shared: Horror · Walking Simulator · Atmospheric

Kholat
Shared: Horror · Atmospheric · Psychological Horror

DISTRAINT: Deluxe Edition
Shared: Indie · Horror · Psychological Horror

Outer Wilds
Shared: Mystery · Exploration · Atmospheric

Fears to Fathom - Carson House
Shared: Horror · Psychological Horror · Atmospheric