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