Here is the full list of all 37 Psychonauts achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
See yourself through the eyes of many others.
Spy on Bobby's love life.
Hear Vernon's Ghost Story.
Cook and consume two different kinds of roast in one sitting.
Buy an item from the Camp Store on Christmas.
Achieve Rank 101.
Complete the Punchy Target mini-game.
Complete Meat Circus.
Gather all Figments.
Sort all Emotional Baggage.
Crack all Vaults.
Complete The Asylum.
Introduce all Camp Kids to Mr. Pokeylope.
Re-brain the Children.
Find all Golden Helmets.
Revisit all brains after completion.
Achieve Rank 80.
Redeem all 16 Scavenger Hunt Items.
Complete Black Velvetopia.
Earn all Merit Badges.
Use the bacon. A lot.
Give the Coach's speech on the stump.
Discover the secret history of Whispering Rock.
Read many bulletin board messages.
Find Edgar's Secret Garden.
Complete Waterloo World.
Achieve Rank 60.
Complete Gloria’s Theater.
Complete The Milkman Conspiracy.
Complete Lungfishopolis.
Achieve Rank 40.
Complete Milla’s Dance Party.
Uncover Milla's Secret.
Achieve Rank 20.
Witness Maloof's transformation.
Complete Sasha’s Shooting Gallery.
Complete Basic Braining.