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